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Kobayashi Tatsuo

Faculty of Science　Physics　Nonlinear PhysicsProfessor

Researcher basic information

■ Degree
  • Ph. D, Master of Science, Kanazawa University
■ URL
researchmap URLホームページURL■ Various IDs
J-Global ID■ Research Keywords and Fields
Research Keyword
  • 超対称性
  • 超弦理論
  • 素粒子論
  • 質量行列
  • 素粒子(理論)
  • フレーバー対称性
  • 超対称性の破れ
  • 湯川結合
  • フレーバー
  • 素
  • 弦理論
  • 余剰次元
  • 素粒子の質量
  • くり込み群
  • 標準模型
  • FCNC
  • 超対称の破れ
  • モジュライ
  • ニュートリノ
  • 超重力理論
  • 大統一理論
  • 世代構造
  • E_6大統一理論
  • オービフォルド
  • 超弦模型
  • ニュートリノ振動
  • 暗黒物質
  • 超対称弦
  • レプジェネシス
  • Leptogenesis
Research Field
  • Natural Science, Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics
■ Educational Organization

Career

■ Career
Educational Background
  • 1991, Kanazawa University, 自然科学研究科, 物理, Japan
  • 1991, Kanazawa University, Graduate School, Division of National Science and Technology
  • 1986, Saitama University, Faculty of Science, 物理, Japan
  • 1986, Saitama University, Faculty of Science

Research activity information

■ Papers
■ Other Activities and Achievements
  • Remark on modular weights in low-energy effective field theory from type II string theory
    Shota Kikuchi; Tatsuo Kobayashi; Kaito Nasu; Hajime Otsuka; Shohei Takada; Hikaru Uchida, Journal of High Energy Physics, 2023, 4, 24 Jan. 2023
  • Quark hierarchical structures in modular symmetric flavor models at level 6
    Shota Kikuchi; Tatsuo Kobayashi; Kaito Nasu; Shohei Takada; Hikaru Uchida, 10 Jan. 2023
    We study modular symmetric quark flavor models without fine-tuning. Mass
    matrices are written in terms of modular forms, and modular forms in the
    vicinity of the modular fixed points become hierarchical depending on their
    residual charges. Thus modular symmetric flavor models in the vicinity of the
    modular fixed points have a possibility to describe mass hierarchies without
    fine-tuning. Since describing quark hierarchies without fine-tuning requires
    $Z_n$ residual symmetry with $n\geq 6$, we focus on $\Gamma_6$ modular symmetry
    in the vicinity of the cusp $\tau=i\infty$ where $Z_6$ residual symmetry
    remains. We use only modular forms belonging to singlet representations of
    $\Gamma_6$ to make our analysis simple. Consequently, viable quark flavor
    models are obtained without fine-tuning.
  • Quark and lepton flavor structure in magnetized orbifold models at residual modular symmetric points
    Kouki Hoshiya; Shota Kikuchi; Tatsuo Kobayashi; Hikaru Uchida, 15 Sep. 2022
    We study quark and lepton mass matrices derived from magnetized
    $T^2/\mathbb{Z}_2$ orbifold models. Quark and lepton masses have a large
    hierarchy. In addition, mixing angles are large in the lepton sector, while
    those are small in the quark sector. We find that this structure can be
    realized in certain flavor models, which are identified by the zero points of
    the zero-mode wave functions of fermions and Higgs modes. We classify such
    realistic flavor models. Fixed points $\tau=i$, $e^{2\pi i/3}$ and $i\infty$ of
    the modulus $\tau$ play a role in realizing a large mass hierarchy through our
    scenario, where residual $S$, $ST$, and $T$ symmetries remain and the lightest
    Higgs modes can correspond to eigenstates of residual symmetries at the leading
    order. As a result, we find that there are 24 flavor models in total which can
    be realistic in a vicinity of $S$-symmetric vacuum but no flavor models for
    $ST$ and $T$-symmetric vacua.
  • Mass matrices with CP phase in modular flavor symmetry
    Shota Kikuchi; Tatsuo Kobayashi; Morimitsu Tanimoto; Hikaru Uchida, 17 Jun. 2022
    We study the CP violation and the CP phase of quark mass matrices in modular
    flavor symmetric models. The CP symmetry remains at $\tau = e^{2 \pi i/3}$ by a
    combination of the $T$-symmetry of the modular symmetry. However, the
    $T$-symmetry breaking may lead to the CP violation at the fixed point $\tau =
    e^{2 \pi i/3}$. We study such a possibility in magnetized orbifold models as
    examples of modular flavor symmetric models. These models, in general, have
    more than one candidates for Higgs modes, while generic string
    compactifications also lead to several Higgs modes. These Higgs modes have
    different behaviors under the $T$-transformation. The light Higgs mode can be a
    linear combination of those modes so as to lead to realistic quark mass
    matrices. The CP phase of mass matrix does not appear in a certain case, which
    is determined by the $T$-transformation behavior. Deviation from it is
    important to realize the physical CP phase. We discuss an example leading to
    non-vanishing CP phase at the fixed point $\tau = e^{2 \pi i/3}$.
  • Modular symmetry of soft supersymmetry breaking terms
    Shota Kikuchi; Tatsuo Kobayashi; Kaito Nasu; Hajime Otsuka; Shohei Takada; Hikaru Uchida, 28 Mar. 2022
    We study the modular symmetry of soft supersymmetry breaking terms. Soft
    scalar masses and $A$-term coefficients are invariant under the modular
    symmetry when we regard $F$-term as a spurion with the modular weight $-2$.
    Their flavor structure is determined by the same symmetry as Yukawa couplings,
    i.e., fermion masses. The modular symmetric behavior of $\mu$-term and $B$-term
    depends on how the $\mu$-term is generated.
  • Modular symmetry anomaly and non-perturbative neutrino mass terms in magnetized orbifold models
    Shota Kikuchi; Tatsuo Kobayashi; Kaito Nasu; Hikaru Uchida; Shohei Uemura, 11 Feb. 2022
    We study the modular symmetry anomaly in magnetized orbifold models. The
    non-perturbative effects such as D-brane instanton effects can break tree-level
    symmetry. We study which part of the modular symmetry is broken explicitly by
    Majorana mass terms with three generations of neutrinos. The modular weight of
    neutrino mass terms does not match with other coupling terms in tree-level
    Lagrangian. In addition, the $Z_N$ symmetry of the modular flavor symmetry is
    broken and a certain normal subgroup of the modular flavor symmetry remains in
    neutrino mass terms.
  • 4D modular flavor symmetric models inspired by higher dimensional theory
    Shota Kikuchi; Tatsuo Kobayashi; Hajime Otsuka; Morimitsu Tanimoto; Hikaru Uchida; Kei Yamamoto, 12 Jan. 2022
    We study a scenario to derive four-dimensional modular flavor symmetric
    models from higher dimensional theory by assuming the compactification
    consistent with the modular symmetry. In our scenario, wavefunctions in extra
    dimensional compact space are modular forms. That leads to constraints on
    combinations between modular weights and $\Gamma_N$ ($\Gamma_N')$
    representations of matter fields. We also present illustrating examples.
  • On stringy origin of minimal flavor violation
    Tatsuo Kobayashi; Hajime Otsuka, European Physical Journal C, 82, 1, Jan. 2022
    Report scientific journal
  • Yukawa textures in modular symmetric vacuum of magnetized orbifold models
    Shota Kikuchi; Tatsuo Kobayashi; Yuya Ogawa; Hikaru Uchida, 03 Dec. 2021
    We study quark mass matrices derived from magnetized $T^2/\mathbb{Z}_2$
    orbifold models. Yukawa matrices at three modular fixed points, $\tau=i,
    e^{2\pi i/3}$ and $i\infty$ are invariant under $S$, $ST$ and
    $T$-transformations. We study these invariances on $T^2/\mathbb{Z}_2$ twisted
    orbifold. We find that Yukawa matrices have a kind of texture structures
    although ones at $\tau=i\infty$ are not realistic. We classify Yukawa textures
    at $\tau=i$ and $e^{2\pi i/3}$. Moreover we investigate the conditions such
    that quark mass matrix constructed by Yukawa textures becomes approximately
    rank one matrix, which is favorable to lead to hierarchical masses between the
    third generation and the others. It is found that realistic quark mass matrices
    can be obtained around the $S$-invariant vacuum and $ST$-invariant vacuum. As
    an illustrating example, we show the realization of the quark mass ratios and
    mixing based on Fritzch and Fritzch-Xing mass matrices.
  • Anomaly of non-Abelian discrete symmetries
    Tatsuo Kobayashi; Hikaru Uchida, 21 Nov. 2021
    We study anomalies of non-Abelian discrete symmetries; which part of
    non-Abelian group is anomaly free and which part can be anomalous. It is found
    that the anomaly-free elements of the group $G$ generate a normal subgroup
    $G_0$ of $G$ and the residue class group $G/G_0$, which becomes the anomalous
    part of $G$, is isomorphic to a single cyclic group. The derived subgroup
    $D(G)$ of $G$ is useful to study the anomaly structure. This structure also
    constrains the structure of the anomaly-free subgroup; the derived subgroup
    $D(G)$ should be included in the anomaly-free subgroup. We study the detail
    structure of the anomaly-free subgroup from the structure of the derived
    subgroup in various discrete groups. For example, when $G=S_n \simeq A_n
    \rtimes Z_2$ and $G=\Delta(6n^2) \simeq \Delta(3n^2) \rtimes Z_2$, in
    particular, $A_n$ and $\Delta(3n^2)$ are at least included in the anomaly-free
    subgroup, respectively. This result holds in any arbitrary representations.
  • Dark matter stability at fixed points in a modular $A_4$ symmetry
    Tatsuo Kobayashi; Hiroshi Okada; Yuta Orikasa, 10 Nov. 2021
    We propose a new mechanism of stabilization for dark matter under fixed
    points of modular $A_4$ symmetry, thanks to recovering a residual symmetry for
    each of fixed points at $\tau=\omega,\ i, i\times\infty$. We find that a model
    at $\tau =i$ successfully reproduces the neutrino oscillation data without
    conflict of the DM stability.
  • Majorana neutrino masses by D-brane instanton effects in magnetized orbifold models
    Kouki Hoshiya; Shota Kikuchi; Tatsuo Kobayashi; Kaito Nasu; Hikaru Uchida; Shohei Uemura, 12 Mar. 2021
    We study Majorana neutrino masses induced by D-brane instanton effects in
    magnetized orbifold models. We classify possible cases, where neutrino masses
    can be induced. Three and four generations are favored in order to generate
    neutrino masses by D-brane instantons. Explicit mass matrices have specific
    features. Their diagonalizing matrices correspond to the bimaximal mixing
    matrix in the case with even magnetic fluxes, independently of the modulus
    value $\tau$. On the other hand, for odd magnetic fluxes, diagonalizing
    matrices correspond nearly to the tri-bimaximal mixing matrix near $\tau =i$,
    while they become the bimaximal mixing matrix for larger ${\rm Im}\tau$. For
    even fluxes, neutrino masses are modular forms of the weight 1 on
    $T^2/\mathbb{Z}_2$, and they have symmetries such as $S_4'$ and
    ${\Delta'}(96)\times \mathbb{Z}_3$.
  • Soft supersymmetry breaking terms and lepton flavor violations in modular flavor models
    Tatsuo Kobayashi; Takashi Shimomura; Morimitsu Tanimoto, 20 Feb. 2021
    We study the soft supersymmetry (SUSY) breaking terms due to the modulus
    F-term in the modular flavor models of leptons. It is found that the soft SUSY
    breaking terms are constrained by the modular forms, and specific patterns are
    derived. Those phenomenological implications are discussed in such as the
    lepton flavor violation, $\mu \rightarrow e + \gamma$ decay. In order to
    examine numerically, two modular flavor $A_4$ models are taken. The SUSY
    breaking scale is significantly constrained by inputting the observed upper
    bound of the $\mu \rightarrow e + \gamma$ decay. The SUSY mass scale is larger
    than around $8$ TeV and $5$ TeV for the two $A_4$ models, respectively.
    Therefore, the current experimental upper bound for the $\mu \to e + \gamma$
    decay corresponds to the new physics of the SUSY particle at the $5$ -- $10$
    TeV scale in the modular flavor models. The predicted branching ratio depends
    on a modulus $\tau$ significantly. It decreases of one order at the large ${\rm
    Im}\,\tau$. We also calculate the branching ratios of tauon decays to $e +
    \gamma$ and $\mu + \gamma$. Predicted ones are at most ${\cal O}(10^{-15})$,
    which are much below the current experimental bounds.
  • Modular flavor symmetries of three-generation modes on magnetized toroidal orbifolds
    Shota Kikuchi; Tatsuo Kobayashi; Hikaru Uchida, 04 Jan. 2021
    We study the modular symmetry on magnetized toroidal orbifolds with
    Scherk-Schwarz phases. In particular, we investigate finite modular flavor
    groups for three-generation modes on magnetized orbifolds. The three-generation
    modes can be the three-dimensional irreducible representations of covering
    groups and central extended groups of $\Gamma_N$ for $N=3,4,5,7,8,16$, that is,
    covering groups of $\Delta(6(N/2)^2)$ for $N=$ even and central extensions of
    $PSL(2,\mathbb{Z}_{N})$ for $N=$odd with Scherk-Schwarz phases. We also study
    anomaly behaviors.
  • Classification of three generation models by orbifolding magnetized $T^2 \times T^2$
    Kouki Hoshiya; Shota Kikuchi; Tatsuo Kobayashi; Yuya Ogawa; Hikaru Uchida, 01 Dec. 2020
    We study orbifolding by the $\mathbb{Z}_2^{\rm (per)}$ permutaion of $T^2_1
    \times T^2_2$ with magnetic fluxes and its twisted orbifolds. We classify the
    possible three generation models which lead to non-vanishing Yukawa couplings
    on the magnetized $T^2_1 \times T^2_2$ and orbifolds including the
    $\mathbb{Z}_2^{\rm (per)}$ permutation and $\mathbb{Z}_2^{\rm (t)}$ twist. We
    also study the modular symmetry on such orbifold models. As an illustrating
    model, we examine the realization of quark masses and mixing angles.
  • Revisiting modular symmetry in magnetized torus and orbifold compactifications
    Shota Kikuchi; Tatsuo Kobayashi; Shintaro Takada; Takuya H. Tatsuishi; Hikaru Uchida, 26 May 2020
    We study the modular symmetry in $T^2$ and orbifold comfactifications with
    magnetic fluxes. There are $|M|$ zero-modes on $T^2$ with the magnetic flux
    $M$. Their wavefunctions as well as massive modes behave as modular forms of
    weight $1/2$ and represent the double covering group of $\Gamma \equiv
    SL(2,\mathbb{Z})$, $\widetilde{\Gamma} \equiv \widetilde{SL}(2,\mathbb{Z})$.
    Each wavefunction on $T^2$ with the magnetic flux $M$ transforms under
    $\widetilde{\Gamma}(2|M|)$, which is the normal subgroup of
    $\widetilde{SL}(2,\mathbb{Z})$. Then, $|M|$ zero-modes are representations of
    the quotient group $\widetilde{\Gamma}'_{2|M|} \equiv
    \widetilde{\Gamma}/\widetilde{\Gamma}(2|M|)$. We also study the modular
    symmetry on twisted and shifted orbifolds $T^2/\mathbb{Z}_N$. Wavefunctions are
    decomposed into smaller representations by eigenvalues of twist and shift. They
    provide us with reduction of reducible representations on $T^2$.
  • Type II seesaw models with modular $A_4$ symmetry
    Tatsuo Kobayashi; Takaaki Nomura; Takashi Shimomura, 02 Dec. 2019
    We discuss type-II seesaw models adopting modular $A_4$ symmetry in
    supersymmetric framework. In our approach, the models are classified by the
    assignment of $A_4$ representations and modular weights for leptons and triplet
    Higgs fields. Then neutrino mass matrix is characterized by modulus $\tau$ and
    two free parameters. Carrying out numerical analysis, we find allowed parameter
    sets which can fit the neutrino oscillation data. For the allowed parameter
    sets, we obtain the predictions in neutrino sector such as CP violating phases
    and the lightest neutrino mass. Finally we also show the predictions for the
    branching ratios of doubly charged scalar boson focusing on the case where the
    doubly charged scalar boson dominantly decays into charged leptons.
  • $CP$ violation in modular invariant flavor models
    Tatsuo Kobayashi; Yusuke Shimizu; Kenta Takagi; Morimitsu Tanimoto; Takuya H. Tatsuishi; Hikaru Uchida, 25 Oct. 2019
    We study the spontaneous $CP$ violation through the stabilization of the
    modulus $\tau$ in modular invariant flavor models. The $CP$-invaraiant
    potentential has the minimum only at ${\rm Re}[\tau] = 0$ or 1/2. From this
    prediction, we study $CP$ violation in modular invariant flavor models. The
    physical $CP$ phase is vanishing. The important point for the $CP$ conservation
    is the $T$ transformation in the modular symmetry. One needs the violation of
    $T$ symmetry to realize the spontaneous $CP$ violation.
  • $A_4$ lepton flavor model and modulus stabilization from $S_4$ modular symmetry
    Tatsuo Kobayashi; Yusuke Shimizu; Kenta Takagi; Morimitsu Tanimoto; Takuya H. Tatsuishi, 09 Sep. 2019
    We study the modulus stabilization in an $A_4$ model whose $A_4$ flavor
    symmetry is originated from the $S_4$ modular symmetry. We can stabilize the
    modulus so that the $A_4$ invariant superpotential leads to the realistic
    lepton masses and mixing angles. We also discuss the phenomenological aspect of
    the present model as a consequence of the modulus stabilization.
  • New $A_4$ lepton flavor model from $S_4$ modular symmetry
    Tatsuo Kobayashi; Yusuke Shimizu; Kenta Takagi; Morimitsu Tanimoto; Takuya H. Tatsuishi, 22 Jul. 2019
    We study a flavor model with $A_4$ symmetry which originates from $S_4$
    modular group. In $S_4$ symmetry, $Z_2$ subgroup can be anomalous, and then
    $S_4$ can be violated to $A_4$. Starting with a $S_4$ symmetric Lagrangian at
    the tree level, the Lagrangian at the quantum level has only $A_4$ symmetry
    when $Z_2$ in $S_4$ is anomalous. We obtain modular forms of two singlets and a
    triplet representations of $A_4$ by decomposing $S_4$ modular forms into $A_4$
    representations. We propose a new $A_4$ flavor model of leptons by using those
    $A_4$ modular forms. We succeed in constructing a viable neutrino mass matrix
    through the Weinberg operator for both normal hierarchy (NH) and inverted
    hierarchy (IH) of neutrino masses. Our predictions of the CP violating Dirac
    phase $\delta_{CP}$ and the mixing $\sin^2\theta_{23}$ depend on the sum of
    neutrino masses for NH.
  • Modular $S_3$ invariant flavor model in SU(5) GUT
    Tatsuo Kobayashi; Yusuke Shimizu; Kenta Takagi; Morimitsu Tanimoto; Takuya H. Tatsuishi, 25 Jun. 2019
    We present a flavor model with the $S_3$ modular invariance in the framework
    of SU(5) GUT. The $S_3$ modular forms of weights $2$ and $4$ give the quark and
    lepton mass matrices with a common complex parameter, the modulus $\tau$. The
    GUT relation of down-type quarks and charged leptons is imposed by the VEV of
    adjoint 24-dimensional Higgs multiplet in addition to the VEVs of $5$ and $\bar
    5$ Higgs multiples of SU(5). The observed CKM and PMNS mixing parameters as
    well as the mass eigenvalues are reproduced properly. We discuss the leptonic
    CP phase and the effective mass of the neutrinoless double beta decay with the
    sum of neutrino masses.
  • Modular symmetry anomaly in magnetic flux compactification
    Yuki Kariyazono; Tatsuo Kobayashi; Shintaro Takada; Shio Tamba; Hikaru Uchida, 16 Apr. 2019
    We study modular symmetry anomalies in four-dimensional low-energy effective
    field theory, which is derived from six-dimensional supersymmetric $U(N)$
    Yang-Mills theory by magnetic flux compactification. The gauge symmetry $U(N)$
    is broken to $U(N_a) \times U(N_b)$ by magnetic fluxes. It is found that
    Abelian subgroup of the modular symmetry corresponding to discrete part of
    $U(1)$ can be anomalous, but other elements independent of $U(1)$ in the
    modular symmetry are always anomaly-free.
  • Finite modular subgroups for fermion mass matrices and baryon/lepton number violation
    Tatsuo Kobayashi; Yusuke Shimizu; Kenta Takagi; Morimitsu Tanimoto; Takuya H. Tatsuishi; Hikaru Uchida, 23 Dec. 2018
    We study a flavor model that the quark sector has the $S_3$ modular
    symmetry,while the lepton sector has the $A_4$ modular symmetry. Our model
    leads to characteristic quark mass matrices which are consistent with
    experimental data of quark masses, mixing angles and the CP violating phase.
    The lepton sector is also consistent with the experimental data of neutrino
    oscillations. We also study baryon and lepton number violations in our flavor
    model.
  • Modular forms of finite modular subgroups from magnetized D-brane models
    Tatsuo Kobayashi; Shio Tamba, 28 Nov. 2018
    We study modular transformation of holomorphic Yukawa couplings in magnetized
    D-brane models. It is found that their products are modular forms, which are
    non-trivial representations of finite modular subgroups, e.g. $S_3$, $S_4$,
    $\Delta(96)$ and $\Delta(384)$.
  • Non-Universal Gaugino Masses in the NMSSM
    Junichiro Kawamura; Tatsuo Kobayashi; Natsumi Nagata, 24 Aug. 2018
    The Next-to-Minimal Supersymmetric Standard Model (NMSSM) provides a natural

    framework to realize a low-scale supersymmetric (SUSY) model, where a singlet

    superfield is added to the minimal model to generate a SUSY-scale higgsino mass

    term with its vacuum expectation value. Due to the presence of the extra

    singlet field, the vacuum conditions to realize the correct electroweak

    symmetry-breaking become fairly restrictive especially if we impose

    universality conditions at the unification scale. In this paper, we show that a

    non-universal gaugino mass spectrum can significantly relax this restriction

    even though the scalar masses and trilinear couplings are subject to

    universality conditions. With the gaugino non-universality, we find that

    higgsino can be the lightest SUSY particle and its thermal relic abundance can

    reproduce the observed dark matter density in a wide range of parameter space

    in which the 125~GeV Higgs-boson mass is obtained. This higgsino-like dark

    matter may be probed in direct detection experiments. We also find that there

    is an upper bound on the masses of supersymmetric particles in this scenario,

    and many model points predict colored particles such as gluino to be within the

    reach of a future 100~TeV collider. Implications for no-scale/gaugino-mediation

    models are also discussed., Technical report
  • Modular $A_4$ invariance and neutrino mixing
    Tatsuo Kobayashi; Naoya Omoto; Yusuke Shimizu; Kenta Takagi; Morimitsu Tanimoto; Takuya H. Tatsuishi, 09 Aug. 2018
    We study the phenomenological implications of the modular symmetry $\Gamma(3)

    \simeq A_4$ of lepton flavors facing recent experimental data of neutrino

    oscillations. The mass matrices of neutrinos and charged leptons are

    essentially given by fixing the expectation value of modulus $\tau$, which is

    the only source of modular invariance breaking. We introduce no flavons in

    contrast with the conventional flavor models with $A_4$ symmetry. We classify

    our neutrino models along with the type I seesaw model, the Weinberg operator

    model and the Dirac neutrino model. In the normal hierarchy of neutrino masses,

    the seesaw model is available by taking account of recent experimental data of

    neutrino oscillations and the cosmological bound of sum of neutrino masses. The

    predicted $\sin^2\theta_{23}$ is restricted to be larger than $0.54$ and

    $\delta_{CP}=\pm (50^{\circ}\mbox{--}180^{\circ})$. Since the correlation of

    $\sin^2\theta_{23}$ and $\delta_{CP}$ is sharp, the prediction is testable in

    the future. It is remarkable that the effective mass $m_{ee}$ of the

    neutrinoless double beta decay is around $22$\,meV while the sum of neutrino

    masses is predicted to be $145$\,meV. On the other hand, for the inverted

    hierarchy of neutrino masses, only the Dirac neutrino model is consistent with

    the experimental data., Technical report
  • Predictive neutrino mass textures with origin of flavor symmetries
    Tatsuo Kobayashi; Takaaki Nomura; Hiroshi Okada, Phys. Rev. D 98, 055025 (2018), 18 May 2018
    We investigate origins of predictive one-zero neutrino mass textures in a

    systematic way. Here we search Abelian continuous(discrete) global symmetries,

    and non-Abelian discrete symmetries, and show how to realize these neutrino

    masses. Then we propose a concrete model involving a dark matter candidate and

    an extra gauge boson, and show their phenomenologies., Technical report
  • Radiative Kähler moduli stabilization RADIATIVE KÄHLER MODULI STABILIZATION KOBAYASHI et al.
    Tatsuo Kobayashi; Naoya Omoto; Hajime Otsuka; Takuya H. Tatsuishi, Physical Review D, 97, 10, 15 May 2018
    American Physical Society, English, Technical report
  • Modular symmetry and non-Abelian discrete flavor symmetries in string compactification
    Tatsuo Kobayashi; Satoshi Nagamoto; Shintaro Takada; Shio Tamba; Takuya H. Tatsuishi, Phys. Rev. D 97, 116002 (2018), 18 Apr. 2018
    We study the modular symmetry in magnetized D-brane models on $T^2$.

    Non-Abelian flavor symmetry $D_4$ in the model with magnetic flux $M=2$ (in a

    certain unit) is a subgroup of the modular symmetry. We also study the modular

    symmetry in heterotic orbifold models. The $T^2/Z_4$ orbifold model has the

    same modular symmetry as the magnetized brane model with $M=2$, and its flavor

    symmetry $D_4$ is a subgroup of the modular symmetry., Technical report
  • Modulus D-term inflation
    Kenji Kadota; Tatsuo Kobayashi; Ikumi Saga; Keigo Sumita, Journal of High Energy Physics, 2018, 4, 01 Apr. 2018
    Springer Verlag, English, Technical report
  • Neutrino mixing from finite modular groups
    Tatsuo Kobayashi; Kentaro Tanaka; Takuya H. Tatsuishi, Phys. Rev. D 98, 016004 (2018), 28 Mar. 2018
    We study the lepton flavor models, whose flavor symmetries are finite

    subgroups of the modular group such as $S_3$ and $A_4$. In our models,

    couplings are also nontrivial representations of these groups and modular

    functions of the modulus. We study the possibilities that these models realize

    realistic values of neutrino masses and lepton mixing angles., Technical report
  • A viable D-term hybrid inflation model
    Kenji Kadota; Tatsuo Kobayashi; Keigo Sumita, Journal of Cosmology and Astroparticle Physics, 2017, 11, 21 Nov. 2017
    Institute of Physics Publishing, English, Technical report
  • Realization of a spontaneous gauge and supersymmetry breaking vacuum
    Tatsuo Kobayashi; Yuji Omura; Osamu Seto; Kazuki Ueda, JOURNAL OF HIGH ENERGY PHYSICS, 11, Nov. 2017
    English, Technical report
  • Zero-modes on orbifolds: Magnetized orbifold models by modular transformation
    Tatsuo Kobayashi; Satoshi Nagamoto, PHYSICAL REVIEW D, 96, 9, Nov. 2017
    English, Technical report
  • Relaxion window
    Tatsuo Kobayashi; Osamu Seto; Takashi Shimomura; Yuko Urakawa, MODERN PHYSICS LETTERS A, 32, 27, Sep. 2017
    English, Technical report
  • Supersymmetry preserving and breaking degenerate vacua, and radiative moduli stabilization
    Tatsuo Kobayashi; Naoya Omoto; Hajime Otsuka; Takuya H. Tatsuishi, PHYSICAL REVIEW D, 96, 4, Aug. 2017
    English, Technical report
  • Kahler moduli stabilization in semirealistic magnetized orbifold models
    Hiroyuki Abe; Tatsuo Kobayashi; Keigo Sumita; Shohei Uemura, PHYSICAL REVIEW D, 96, 2, Jul. 2017
    English, Technical report
  • Polyinstanton axion inflation
    Tatsuo Kobayashi; Shohei Uemura; Junji Yamamoto, PHYSICAL REVIEW D, 96, 2, Jul. 2017
    English, Technical report
  • Axion inflation and Affleck-Dine baryogenesis
    Kensuke Akita; Tatsuo Kobayashi; Hajime Otsuka, JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, 4, Apr. 2017
    English, Technical report
  • CP-violating phase on magnetized toroidal orbifolds
    Tatsuo Kobayashi; Kenji Nishiwaki; Yoshiyuki Tatsuta, JOURNAL OF HIGH ENERGY PHYSICS, 4, Apr. 2017
    English, Technical report
  • Toward pole inflation and attractors in supergravity : Chiral matter field inflation
    Tatsuo Kobayashi; Osamu Seto; Takuya H. Tatsuishi, 29 Mar. 2017
    In string-inspired supergravity theory, K\"{a}hler metric of chiral matter

    fields often has a pole. Such K\"{a}hler metric is interesting from the

    viewpoint of the framework of the pole inflation, where the scalar potential

    can be stretched out to be flat around the pole for a canonically normalized

    field and inflation can be realized. However, when K\"{a}hler metric has a

    pole, the scalar potential can also have a pole at the same point in

    supergravity theory. We study such supergravity models with the pole, and

    provide numerical analysis of inflationary dynamics and resultant density

    perturbation. In contrast with usual pole inflation models, inflation in this

    supergravity based model occurs not on the pole but region apart from the pole.

    We show that the existence of the pole in the scalar potential is crucial

    nevertheless. We also examine attractor behavior of our model., Technical report
  • Constraints on small-field axion inflation
    Tatsuo Kobayashi; Akane Oikawa; Naoya Omoto; Hajime Otsuka; Ikumi Saga, PHYSICAL REVIEW D, 95, 6, Mar. 2017
    English, Technical report
  • Supersymmetric models on magnetized orbifolds with flux-induced Fayet-Iliopoulos terms
    Hiroyuki Abe; Tatsuo Kobayashi; Keigo Sumita; Yoshiyuki Tatsuta, PHYSICAL REVIEW D, 95, 1, Jan. 2017
    English, Technical report
  • Flavor structure in SO(32) heterotic string theory
    Hiroyuki Abe; Tatsuo Kobayashi; Hajime Otsuka; Yasufumi Takano; Takuya H. Tatsuishi, PHYSICAL REVIEW D, 94, 12, Dec. 2016
    English, Technical report
  • Small field axion inflation with sub-Planckian decay constant
    Kenji Kadota; Tatsuo Kobayashi; Akane Oikawa; Naoya Omoto; Hajime Otsuka; Takuya H. Tatsuishi, JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, 10, Oct. 2016
    English, Technical report
  • Dynamical supersymmetry breaking on magnetized tori and orbifolds
    Hiroyuki Abe; Tatsuo Kobayashi; Keigo Sumita, NUCLEAR PHYSICS B, 911, 606, 622, Oct. 2016
    English, Technical report
  • Dilaton stabilization in three-generation heterotic string model
    Florian Beye; Tatsuo Kobayashi; Shogo Kuwakino, PHYSICS LETTERS B, 760, 63, 68, Sep. 2016
    English, Technical report
  • Modular symmetry in magnetized/intersecting D-brane models
    Tatsuo Kobayashi; Satoshi Nagamoto; Shohei Uemura, 22 Aug. 2016
    We study the modular symmetry in four-dimensional low-energy effective field

    theory, which is derived from type IIB magnetized D-brane models and type IIA

    intersecting D-brane models. We analyze modular symmetric behaviors of

    perturbative terms and non-perturbative terms induced by D-brane instanton

    effects. Anomalies are also investigated and such an analysis on anomalies

    suggests corrections in effective field theory., Technical report
  • Comprehensive analysis of Yukawa hierarchies on T-2/Z(N) with magnetic fluxes
    Yukihiro Fujimoto; Tatsuo Kobayashi; Kenji Nishiwaki; Makoto Sakamoto; Yoshiyuki Tatsuta, PHYSICAL REVIEW D, 94, 3, Aug. 2016
    English, Technical report
  • Modular invariant inflation
    Tatsuo Kobayashi; Daisuke Nitta; Yuko Urakawa, JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, 8, Aug. 2016
    English, Technical report
  • Gauge coupling unification in SO(32) heterotic string theory with magnetic fluxes
    Hiroyuki Abe; Tatsuo Kobayashi; Hajime Otsuka; Yasufumi Takano; Takuya H. Tatsuishi, PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS, 5, May 2016
    English, Technical report
  • Moduli mediation without moduli-induced gravitino problem
    Kensuke Akita; Tatsuo Kobayashi; Akane Oikawa; Hajime Otsuka, JOURNAL OF HIGH ENERGY PHYSICS, 5, May 2016
    English, Technical report
  • New potentials for string axion inflation
    Tatsuo Kobayashi; Akane Oikawa; Hajime Otsuka, PHYSICAL REVIEW D, 93, 8, Apr. 2016
    English, Technical report
  • Majorana neutrino mass structure induced by rigid instantons on toroidal orbifold
    Tatsuo Kobayashi; Yoshiyuki Tatsuta; Shohei Uemura, PHYSICAL REVIEW D, 93, 6, Mar. 2016
    English, Technical report
  • Phenomenology of NMSSM in TeV scale mirage mediation
    Kei Hagimoto; Tatsuo Kobayashi; Hiroki Makino; Ken-ichi Okumura; Takashi Shimomura, JOURNAL OF HIGH ENERGY PHYSICS, 2, Feb. 2016
    English, Technical report
  • Axion inflation with cross-correlated axion isocurvature perturbations
    Kenji Kadota; Tatsuo Kobayashi; Hajime Otsuka, JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, 1, Jan. 2016
    English, Technical report
  • Entropy production by domain wall decay in the NMSSM
    Hironori Hattori; Tatsuo Kobayashi; Naoya Omoto; Osamu Seto, PHYSICAL REVIEW D, 92, 10, Nov. 2015
    English, Technical report
  • Realistic three-generation models from SO (32) heterotic string theory
    Hiroyuki Abe; Tatsuo Kobayashi; Hajime Otsuka; Yasufumi Takano, JOURNAL OF HIGH ENERGY PHYSICS, 9, Sep. 2015
    English, Technical report
  • Standard model-like D-brane models and gauge couplings
    Yuta Hamada; Tatsuo Kobayashi; Shohei Uemura, NUCLEAR PHYSICS B, 897, 563, 582, Aug. 2015
    English, Technical report
  • Dilution of axion dark radiation by thermal inflation
    Hironori Hattori; Tatsuo Kobayashi; Naoya Omoto; Osamu Seto, PHYSICAL REVIEW D, 92, 2, Jul. 2015
    English, Technical report
  • D-brane instanton induced mu terms and their hierarchical structure
    Hiroyuki Abe; Tatsuo Kobayashi; Yoshiyuki Tatsuta; Shohei Uemura, PHYSICAL REVIEW D, 92, 2, Jul. 2015
    English, Technical report
  • Beginning of Universe through large field hybrid inflation
    Tatsuo Kobayashi; Osamu Seto, MODERN PHYSICS LETTERS A, 30, 21, Jul. 2015
    English, Technical report
  • Towards natural inflation from weakly coupled heterotic string theory
    Hiroyuki Abe; Tatsuo Kobayashi; Hajime Otsuka, PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS, 6, Jun. 2015
    English, Technical report
  • Study of lepton flavor violation in flavor symmetric models for lepton sector
    Tatsuo Kobayashi; Yuji Omura; Fumihiro Takayama; Daiki Yasuhara, 28 May 2015
    Flavor symmetric model is one of the attractive Beyond Standard Models (BSMs)

    to reveal the flavor structure of the Standard Model (SM). A lot of efforts

    have been put into the model building and we find many kinds of flavor

    symmetries and setups are able to explain the observed fermion mass matrices.

    In this paper, we look for common predictions of physical observables among the

    ones in flavor symmetric models, and try to understand how to test flavor

    symmetry in experiments. Especially, we focus on the BSMs for leptons with

    extra Higgs $SU(2)_L$ doublets charged under flavor symmetry. In many flavor

    models for leptons, remnant symmetry is partially respected after the flavor

    symmetry breaking, and it controls well the Flavor Changing Neutral Currents

    (FCNCs) and suggests some crucial predictions against the flavor changing

    process, although the remnant symmetry is not respected in the full lagrangian.

    In fact, we see that $\tau^- \to e^+ \mu^- \mu^-$ $( \mu^+ e^- e^-)$ and $e^+

    e^- \to \tau^+\tau^-$ $(\mu^-\mu^+)$ processes are the most important in the

    flavor models that the extra Higgs doublets belong to triplet representation of

    flavor symmetry. For instance, the stringent constraint from the $\mu \to e

    \gamma$ process could be evaded according to the partial remnant symmetry. We

    also investigate the breaking effect of the remnant symmetry mediated by the

    Higgs scalars, and investigate the constraints from the flavor physics: the

    flavor violating $\tau$ and $\mu$ decays, the electric dipole moments, and the

    muon anomalous magnetic moment. We also discuss the correlation between FCNCs

    and nonzero $\theta_{13}$, and point out the physical observables in the

    charged lepton sector to test the BSMs for the neutrino mixing., Technical report
  • Classification of three-generation models on magnetized orbifolds
    Tomo-hiro Abe; Yukihiro Fujimoto; Tatsuo Kobayashi; Takashi Miura; Kenji Nishiwaki; Makoto Sakamoto; Yoshiyuki Tatsuta, NUCLEAR PHYSICS B, 894, 374, 406, May 2015
    English, Technical report
  • Natural inflation with and without modulations in type IIB string theory
    Hiroyuki Abe; Tatsuo Kobayashi; Hajime Otsuka, JOURNAL OF HIGH ENERGY PHYSICS, 4, Apr. 2015
    English, Technical report
  • Gauge extension of non-Abelian discrete flavor symmetry
    Florian Beye; Tatsuo Kobayashi; Shogo Kuwakino, JOURNAL OF HIGH ENERGY PHYSICS, 3, Mar. 2015
    English, Technical report
  • Unification of SUSY breaking and GUT breaking
    Tatsuo Kobayashi; Yuji Omura, JOURNAL OF HIGH ENERGY PHYSICS, 2, 1, 24, Feb. 2015
    English, Technical report
  • Operator analysis of physical states on magnetized T-2/Z(N) orbifolds
    Tomo-hiro Abe; Yukihiro Fujimoto; Tatsuo Kobayashi; Takashi Miura; Kenji Nishiwaki; Makoto Sakamoto, NUCLEAR PHYSICS B, 890, 442, 480, Jan. 2015
    English, Technical report
  • Gaussian Froggatt-Nielsen mechanism on magnetized orbifolds
    Hiroyuki Abe; Tatsuo Kobayashi; Keigo Sumita; Yoshiyuki Tatsuta, PHYSICAL REVIEW D, 90, 10, Nov. 2014
    English, Technical report
  • Revisiting discrete dark matter model: theta(13) not equal 0 and v(R) dark matter
    Yuta Hamada; Tatsuo Kobayashi; Atsushi Ogasahara; Yuji Omura; Fumihiro Takayama; Daiki Yasuhara, JOURNAL OF HIGH ENERGY PHYSICS, 10, Oct. 2014
    English, Technical report
  • Axion monodromy inflation with multi-natural modulations
    Tetsutaro Higaki; Tatsuo Kobayashi; Osamu Seto; Yuya Yamaguchi, JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, 10, Oct. 2014
    English, Technical report
  • Axion monodromy inflation with sinusoidal corrections
    Tatsuo Kobayashi; Osamu Seto; Yuya Yamaguchi, PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS, 10, Oct. 2014
    English, Technical report
  • Gauge origin of discrete flavor symmetries in heterotic orbifolds
    Florian Beye; Tatsuo Kobayashi; Shogo Kuwakino, PHYSICS LETTERS B, 736, 433, 437, Sep. 2014
    English, Technical report
  • 21pSF-4 Gauge coupling constant of D-brane models and its constraints
    Uemura Shohei; Kobayashi Tatsuo; Hamada Yuta, Meeting abstracts of the Physical Society of Japan, 69, 2, 16, 16, 22 Aug. 2014
    The Physical Society of Japan (JPS), Japanese
  • Non-Abelian discrete flavor symmetries of 10D SYM theory with magnetized extra dimensions
    Hiroyuki Abe; Tatsuo Kobayashi; Hiroshi Ohki; Keigo Sumita; Yoshiyuki Tatsuta, JOURNAL OF HIGH ENERGY PHYSICS, 6, Jun. 2014
    English, Technical report
  • Flavor structure in D-brane models: Majorana neutrino masses
    Yuta Hamada; Tatsuo Kobayashi; Shohei Uemura, JOURNAL OF HIGH ENERGY PHYSICS, 5, May 2014
    English, Technical report
  • Polynomial inflation models after BICEP2
    Tatsuo Kobayashi; Osamu Seto, PHYSICAL REVIEW D, 89, 10, May 2014
    English, Technical report
  • Flavor landscape of 10D SYM theory with magnetized extra dimensions
    Hiroyuki Abe; Tatsuo Kobayashi; Hiroshi Ohki; Keigo Sumita; Yoshiyuki Tatsuta, JOURNAL OF HIGH ENERGY PHYSICS, 4, Apr. 2014
    English, Technical report
  • 28pSB-4 Non-pertubative aspects and phenomilogical implication in semi-realistic D-brane model
    Uemura Shohei; Kobayashi Tatsuo; Hamada Yuta, Meeting abstracts of the Physical Society of Japan, 69, 1, 12, 12, 05 Mar. 2014
    The Physical Society of Japan (JPS), Japanese
  • Gaussian textures of Yukawa couplings from magnetized extra dimensions
    ABE HIROYUKI; KOBAYASHI TATSUO; OKI HIROSHI; SUMITA KEIGO; TATSUTA YOSHIYUKI, 日本物理学会講演概要集, 69, 1, 13, 13, 05 Mar. 2014
    The Physical Society of Japan (JPS), Japanese
  • ZN twisted orbifold with magnetic flux in operator formalism
    ABE TOMOHIRO; FUJIMOTO NORIHIRO; KOBAYASHI TATSUO; MIURA TAKASHI; NISHIWAKI KENJI; SAKAMOTO MAKOTO, 日本物理学会講演概要集, 69, 1, 12, 12, 05 Mar. 2014
    The Physical Society of Japan (JPS), Japanese
  • 実現的なDブレーンモデルにおける非摂動効果とその現象論的側面
    上村尚平; 小林達夫; 濱田雄太, 日本物理学会講演概要集, 69, 1, 12, 05 Mar. 2014
    Japanese
  • モジュライインフレーションでの大域的磁場生成並びに曲率揺らぎの非ガウス性とテンソル/スカラー比
    馬塲一晴; 小林達夫; 瀬戸治, 日本物理学会講演概要集, 69, 1, 124, 124, 05 Mar. 2014
    The Physical Society of Japan (JPS), Japanese
  • Discrete R-symmetries and anomaly universality in heterotic orbifolds
    Nana G. Cabo Bizet; Tatsuo Kobayashi; Damian K. Mayorga Pena; Susha L. Parameswaran; Matthias Schmitz; Ivonne Zavala, JOURNAL OF HIGH ENERGY PHYSICS, 2, Feb. 2014
    English, Technical report
  • Z (N) twisted orbifold models with magnetic flux
    Tomo-hiro Abe; Yukihiro Fujimoto; Tatsuo Kobayashi; Takashi Miura; Kenji Nishiwaki; Makoto Sakamoto, JOURNAL OF HIGH ENERGY PHYSICS, 1, Jan. 2014
    English, Technical report
  • Three-generation asymmetric orbifold models from heterotic string theory
    Florian Beye; Tatsuo Kobayashi; Shogo Kuwakino, JOURNAL OF HIGH ENERGY PHYSICS, 1, Jan. 2014
    English, Technical report
  • More on cosmological constraints on spontaneous R-symmetry breaking models
    Yuta Hamada; Kohei Kamada; Tatsuo Kobayashi; Yutaka Ookouchi, JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, 1, Jan. 2014
    English, Technical report
  • CKM matrix and flavor symmetries
    Takeshi Araki; Hiroyuki Ishida; Hajime Ishimori; Tatsuo Kobayashi; Atsushi Ogasahara, PHYSICAL REVIEW D, 88, 9, Nov. 2013
    English, Technical report
  • Gauge symmetries in heterotic asymmetric orbifolds
    Florian Beye; Tatsuo Kobayashi; Shogo Kuwakino, NUCLEAR PHYSICS B, 875, 3, 599, 620, Oct. 2013
    English, Technical report
  • 20aSF-9 Non-Abelian discrete flavor symmetry from magnetized extra dimensions
    安倍 博之; 小林 達夫; 大木 洋; 角田 慶吾; 龍田 佳幸, Meeting abstracts of the Physical Society of Japan, 68, 2, 1, 1, 26 Aug. 2013
    The Physical Society of Japan (JPS), Japanese
  • Non-Abelian discrete flavor symmetry from magnetized extra dimensions
    ABE HIROYUKI; KOBAYASHI TATSUO; OKI HIROSHI; TSUNODA KEIGO; TATSUTA YOSHIYUKI, 日本物理学会講演概要集, 68, 2, 1, 1, 26 Aug. 2013
    The Physical Society of Japan (JPS), Japanese
  • 有限群と素粒子物理学 (特集 群と物理学 : 代数構造を用いて物理を知るために)
    小林 達夫, 数理科学, 51, 7, 51, 56, Jul. 2013
    サイエンス社, Japanese
  • 群と物理学 有限群と素粒子物理学
    小林達夫, 数理科学, 51, 7, 51, 56, 01 Jul. 2013
    サイエンス社, Japanese
  • R-charge conservation and more in factorizable and non-factorizable orbifolds
    Nana G. Cabo Bizet; Tatsuo Kobayashi; Damian K. Mayorga Pena; Susha L. Parameswaran; Matthias Schmitz; Ivonne Zavala, JOURNAL OF HIGH ENERGY PHYSICS, 5, May 2013
    English, Technical report
  • Phenomenological aspects of 10D SYM theory with magnetized extra dimensions
    Hiroyuki Abe; Tatsuo Kobayashi; Hiroshi Ohki; Akane Oikawa; Keigo Sumita, NUCLEAR PHYSICS B, 870, 1, 30, 54, May 2013
    English, Technical report
  • Cosmic R-string in thermal history
    Kohei Kamada; Tatsuo Kobayashi; Keisuke Ohashi; Yutaka Ookouchi, JOURNAL OF HIGH ENERGY PHYSICS, 5, May 2013
    English, Technical report
  • Shifted orbifold models with magnetic flux
    Yukihiro Fujimoto; Tatsuo Kobayashi; Takashi Miura; Kenji Nishiwaki; Makoto Sakamoto, Physical Review D - Particles, Fields, Gravitation and Cosmology, 87, 8, 08 Apr. 2013
    English, Technical report
  • Instability of colliding metastable strings
    Takashi Hiramatsu; Minoru Eto; Kohei Kamada; Tatsuo Kobayashi; Yutaka Ookouchi, 02 Apr. 2013
    The breaking of $U(1)_R$ symmetry plays a crucial role in modeling the

    breaking of supersymmetry (SUSY). In the models that possess both SUSY

    preserving and SUSY breaking vacua, tube-like cosmic strings called R-tubes,

    whose surfaces are constituted by domain walls interpolating a false and a true

    vacuum with some winding numbers, can exist. Their (in)stability can strongly

    constrain SUSY breaking models theirselves. In the present study, we

    investigate the dynamical (in)stability of two colliding metastable tube-like

    strings by field-theoretic simulations. From them, we find that the strings

    become unstable, depending on the relative collision angle and speed of two

    strings, and the false vacuum is eventually filled out by the true vacuum owing

    to rapid expansion of the strings or unstable bubbles created as remnants of

    the collision., Technical report
  • 27aRA-7 Three generations on shifted orbifold with magnetic flux
    Fujimoto Yukihiro; Miura Takashi; Sakamoto Makoto; Kobayashi Tatsuo; Nishiwaki Kenji, Meeting abstracts of the Physical Society of Japan, 68, 1, 7, 7, 26 Mar. 2013
    The Physical Society of Japan (JPS), Japanese
  • 27aRA-5 Flavor landscape of 10D SYM theory with general magnetic fluxes
    安倍 博之; 小林 達夫; 角田 慶吾; 龍田 佳幸, Meeting abstracts of the Physical Society of Japan, 68, 1, 6, 6, 26 Mar. 2013
    The Physical Society of Japan (JPS), Japanese
  • Flavor landscape of 10D SYM theory with general magnetic fluxes
    ABE HIROYUKI; KOBAYASHI TATSUO; SUMITA KEIGO; TATSUTA YOSHIYUKI, 日本物理学会講演概要集, 68, 1, 6, 05 Mar. 2013
    Japanese
  • Three generations on shifted orbifold with magnetic flux
    FUJIMOTO YUKIHIRO; MIURA TAKASHI; SAKAMOTO MAKOTO; KOBAYASHI TATSUO; NISHIWAKI KENJI, 日本物理学会講演概要集, 68, 1, 7, 05 Mar. 2013
    Japanese
  • Cosmic R-string, R-tube and vacuum instability
    Minoru Eto; Yuta Hamada; Kohei Kamada; Tatsuo Kobayashi; Keisuke Ohashi; Yutaka Ookouchi, JOURNAL OF HIGH ENERGY PHYSICS, 3, Mar. 2013
    English, Technical report
  • TeV scale mirage mediation in NMSSM
    Tatsuo Kobayashi; Hiroki Makino; Ken-Ichi Okumura; Takashi Shimomura; Tsubasa Takahashi, Journal of High Energy Physics, 2013, 1, 2013
    English, Technical report
  • TeV scale mirage mediation in NMSSM
    Tatsuo Kobayashi; Hiroki Makino; Ken-Ichi Okumura; Takashi Shimomura; Tsubasa Takahashi, Journal of High Energy Physics, 2013, 1, 2013
    English, Technical report
  • Cosmological constraints on spontaneous R-symmetry breaking models
    Yuta Hamada; Kohei Kamada; Tatsuo Kobayashi; Yutaka Ookouchi, JCAP 1304 (2013) 043, 24 Nov. 2012
    We study general constraints on spontaneous R-symmetry breaking models coming

    from the cosmological effects of the pseudo Nambu-Goldstone bosons, R-axions.

    They are substantially produced in the early Universe and may cause several

    cosmological problems. We focus on relatively long-lived R-axions and find that

    in a wide range of parameter space, models are severely constrained. In

    particular, R-axions with mass less than 1 MeV are generally ruled out for

    relatively high reheating temperature, $T_R>10$ GeV., Technical report
  • Runaway, D term and R-symmetry breaking
    Tatsuo Azeyanagi; Tatsuo Kobayashi; Atsushi Ogasahara; Koichi Yoshioka, PHYSICAL REVIEW D, 86, 9, Nov. 2012
    English, Technical report
  • Massive modes in magnetized brane models
    Yuta Hamada; Tatsuo Kobayashi, Progress of Theoretical Physics, 128, 5, 903, 923, Nov. 2012
    English, Technical report
  • Superfield description of 10D SYM theory with magnetized extra dimensions
    Hiroyuki Abe; Tatsuo Kobayashi; Hiroshi Ohki; Keigo Sumita, NUCLEAR PHYSICS B, 863, 1, 1, 18, Oct. 2012
    English, Technical report
  • Constraining the Higgs sector from false vacua in the next-to-minimal supersymmetric standard model
    Tatsuo Kobayashi; Takashi Shimomura; Tsubasa Takahashi, PHYSICAL REVIEW D, 86, 1, Jul. 2012
    English, Technical report
  • Lepton flavor models with discrete values of theta(13)
    Hajime Ishimori; Tatsuo Kobayashi, PHYSICAL REVIEW D, 85, 12, Jun. 2012
    English, Technical report
  • Revisiting coupling selection rules in heterotic orbifold models
    Tatsuo Kobayashi; Susha L. Parameswaran; Saul Ramos-Sanchez; Ivonne Zavala, JOURNAL OF HIGH ENERGY PHYSICS, 5, May 2012
    English, Technical report
  • 24pGA-13 Low-energy analysis of magnetized SYM
    Abe Hiroyuki; Oikawa Akane; Oki Hiroshi; Kobayasi Tatsuo; Sumita Keigo, Meeting abstracts of the Physical Society of Japan, 67, 1, 9, 9, 05 Mar. 2012
    The Physical Society of Japan (JPS), Japanese
  • 24pGA-12 The analysis of quark/lepton matrices in high dimensional model with magnetic fluxes and wilson lines
    Abe Hiroyuki; Oikawa Akane; Ohki Hiroshi; Kobayashi Tatsuo; Sumita Keigo; Nomoto Yuki, Meeting abstracts of the Physical Society of Japan, 67, 1, 9, 9, 05 Mar. 2012
    The Physical Society of Japan (JPS), Japanese
  • Low-energy analysis of magnetized SYM
    ABE HIROYUKI; OIKAWA AKANE; OKI HIROSHI; KOBAYASHI TATSUO; SUMITA KEIGO, 日本物理学会講演概要集, 67, 1, 9, 9, 05 Mar. 2012
    The Physical Society of Japan (JPS), Japanese
  • 磁場とウィルソンラインを用いた高次元模型におけるクォーク・レプトン質量行列の解析
    安倍博之; 及川茜; 大木洋; 小林達夫; 角田慶吾; 野本優樹, 日本物理学会講演概要集, 67, 1, 9, 9, 05 Mar. 2012
    The Physical Society of Japan (JPS), Japanese
  • Constraints from unrealistic vacua in the next-to-minimal supersymmetric standard model
    Yoshimi Kanehata; Tatsuo Kobayashi; Yasufumi Konishi; Osamu Seto; Takashi Shimomura, Progress of Theoretical Physics, 126, 6, 1051, 1076, Dec. 2011
    English, Technical report
  • Towards minimal S-4 lepton flavor model
    Hajime Ishimori; Tatsuo Kobayashi, JOURNAL OF HIGH ENERGY PHYSICS, 10, Oct. 2011
    English, Technical report
  • NON-ABELIAN DISCRETE FLAVOR SYMMETRIES ON ORBIFOLDS
    Hiroyuki Abe; Kang-Sin Choi; Tatsuo Kobayashi; Hiroshi Ohki; Manabu Sakai, INTERNATIONAL JOURNAL OF MODERN PHYSICS A, 26, 23, 4067, 4082, Sep. 2011
    English, Technical report
  • Note on moduli stabilization, supersymmetry breaking, and axiverse
    Tetsutaro Higaki; Tatsuo Kobayashi, PHYSICAL REVIEW D, 84, 4, Aug. 2011
    English, Technical report
  • String theory and the real world
    Kane Gordon; 小林 達夫, Parity., 26, 8, 22, 29, Aug. 2011
    丸善, Japanese
  • D term and gaugino masses in gauge mediation
    Tatsuo Azeyanagi; Tatsuo Kobayashi; Atsushi Ogasahara; Koichi Yoshioka, 15 Jun. 2011
    We systematically study supersymmetry breaking with non-vanishing F and D

    terms. We classify the models into two categories and find that a certain class

    of models necessarily has runaway behavior of scalar potential, while the other

    needs the Fayet-Iliopoulos term to break supersymmetry. The latter class is

    useful to have a simple model of gauge mediation where the vacuum is stable

    everywhere and the gaugino mass is generated at the one-loop order., Technical report
  • (Extra)ordinary gauge/anomaly mediation
    Tatsuo Kobayashi; Yuichiro Nakai; Manabu Sakai, JOURNAL OF HIGH ENERGY PHYSICS, 6, Jun. 2011
    English, Technical report
  • Constraints from Unrealistic Vacua in NMSSM
    Konishi Yasufumi; Kanehata Yoshimi; Kobayashi Tatsuo; Seto Osamu; Shimomura Takashi, Soryushiron Kenkyu Electronics, 119, 3, C32, 2011
    Soryushiron Kenkyu Editorial Office, English
  • Inflation, moduli (de)stabilization and supersymmetry breaking
    Tatsuo Kobayashia; Manabu Sakaib, Journal of High Energy Physics, 2011, 4, 2011
    English, Technical report
  • Constraints from unrealistic vacua in the supersymmetric standard model with neutrino mass operators
    Yoshimi Kanehata; Tatsuo Kobayashi; Yasufumi Konishi; Takashi Shimomura, PHYSICAL REVIEW D, 82, 7, Oct. 2010
    English, Technical report
  • Towards the MSSM from F-theory
    Kang-Sin Choi; Tatsuo Kobayashi, PHYSICS LETTERS B, 693, 3, 330, 333, Oct. 2010
    English, Technical report
  • Revisiting superparticle spectra in superconformal flavor models
    Tatsuo Kobayashi; Yuichiro Nakai; Ryo Takahashi, JOURNAL OF HIGH ENERGY PHYSICS, 9, Sep. 2010
    English, Technical report
  • 磁場を持つ高次元超対称模型の4次元有効理論について
    安倍博之; 大木洋; 久能秀幸; 小林達夫; 阪村豊; 角田慶吾, 日本物理学会講演概要集, 65, 2, 9, 9, 18 Aug. 2010
    The Physical Society of Japan (JPS), Japanese
  • Constraints from color and/or charge breaking minima in the supersymmetric standard model with right-handed neutrinos
    Tatsuo Kobayashi; Takashi Shimomura, Physical Review D - Particles, Fields, Gravitation and Cosmology, 82, 3, 12 Aug. 2010
    English, Technical report
  • E (6,7,8) magnetized extra-dimensional models
    Kang-Sin Choi; Tatsuo Kobayashi; Ryosuke Maruyama; Masaki Murata; Yuichiro Nakai; Hiroshi Ohki; Manabu Sakai, EUROPEAN PHYSICAL JOURNAL C, 67, 1-2, 273, 282, May 2010
    English, Technical report
  • Δ(54)対称性によるレプトン,スレプトン質量行列
    石森一; 岡田寛; 小林達夫; 清水勇介; 谷本盛光, 日本物理学会講演概要集, 65, 1, 7, 7, 01 Mar. 2010
    The Physical Society of Japan (JPS), Japanese
  • Flavor structure from magnetic fluxes and non-Abelian Wilson lines
    Hiroyuki Abe; Kang-Sin Choi; Tatsuo Kobayashi; Hiroshi Ohki, 12 Jan. 2010
    We study the flavor structure of 4D effective theories, which are derived

    from extra dimensional theories with magnetic fluxes and non-Abelian Wilson

    lines. We study zero-mode wavefunctions and compute Yukawa couplings as well as

    four-point couplings. In our models, we also discuss non-Abelian discrete

    flavor symmetries such as $D_4$, $\Delta(27)$ and $\Delta(54)$., Technical report
  • Non-Abelian Discrete Symmetries in Particle Physics
    Hajime Ishimori; Tatsuo Kobayashi; Hiroshi Ohki; Yusuke Shimizu; Hiroshi Okada; Morimitsu Tanimoto, PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT, 183, 1, 163, 2010
    English, Technical report
  • Three-generation models from E 8 magnetized extra dimensional theory
    Tatsuo Kobayashi; Ryosuke Maruyama; Masaki Murata; Hiroshi Ohki; Manabu Sakai, Journal of High Energy Physics, 2010, 5, 2010
    English, Technical report
  • Fine tuning in general gauge mediation
    Tatsuo Kobayashi; Yuichiro Nakai; Ryo Takahashi, JOURNAL OF HIGH ENERGY PHYSICS, 1, Jan. 2010
    English, Technical report
  • Magnetic flux, Wilson line, and orbifold
    Hiroyuki Abe; Kang-Sin Choi; Tatsuo Kobayashi; Hiroshi Ohki, PHYSICAL REVIEW D, 80, 12, Dec. 2009
    English, Technical report
  • Delta(54) flavor model for leptons and sleptons
    Hajime Ishimori; Tatsuo Kobayashi; Hiroshi Okada; Yusuke Shimizu; Morimitsu Tanimoto, JOURNAL OF HIGH ENERGY PHYSICS, 12, Dec. 2009
    English, Book review
  • Non-Abelian discrete flavor symmetries from magnetized/intersecting brane models
    Hiroyuki Abe; Kang-Sin Choi; Tatsuo Kobayashi; Hiroshi Ohki, NUCLEAR PHYSICS B, 820, 1-2, 317, 333, Oct. 2009
    English, Technical report
  • オービフォールド化によるΔ(54)フレーバー対称性モデル
    石森一; 岡田寛; 小林達夫; 清水勇介; 谷本盛光, 日本物理学会講演概要集, 64, 2, 9, 9, 18 Aug. 2009
    一般社団法人日本物理学会, Japanese
  • Higher order couplings in magnetized brane models
    Hiroyuki Abe; Kang-Sin Choi; Tatsuo Kobayashi; Hiroshi Ohki, JOURNAL OF HIGH ENERGY PHYSICS, 6, Jun. 2009
    English, Technical report
  • Three generation magnetized orbifold models
    Hiroyuki Abe; Kang-Sin Choi; Tatsuo Kobayashi; Hiroshi Ohki, NUCLEAR PHYSICS B, 814, 1-2, 265, 292, Jun. 2009
    English, Technical report
  • Lepton flavor model from Delta(54) symmetry
    Hajime Ishimori; Tatsuo Kobayashi; Hiroshi Okada; Yusuke Shimizu; Morimitsu Tanimoto, JOURNAL OF HIGH ENERGY PHYSICS, 4, Apr. 2009
    English, Technical report
  • Lepton Flavor Model from .DELTA.(54) Symmetry
    ISHIMORI HAJIME; KOBAYASHI TATSUO; OKADA HIROSHI; SHIMIZU YUSUKE; TANIMOTO MORIMITSU, 日本物理学会講演概要集, 64, 1, 9, 9, 03 Mar. 2009
    The Physical Society of Japan (JPS), Japanese
  • Soft supersymmetry breaking terms from A4 lepton flavor symmetry
    ISHIMORI HAJIME; KOBAYASHI TATSUO; OMURA YUJI; TANIMOTO MORIMITSU, 日本物理学会講演概要集, 64, 1, 18, 18, 03 Mar. 2009
    The Physical Society of Japan (JPS), Japanese
  • Duality cascade of softly broken supersymmetric theories
    Hiroyuki Abe; Tetsutaro Higaki; Tatsuo Kobayashi; Kazutoshi Ohta; Yuji Omura; Haruhiko Terao, PHYSICAL REVIEW D, 79, 4, Feb. 2009
    English, Technical report
  • (Non-)Abelian discrete anomalies
    Takeshi Araki; Tatsuo Kobayashi; Jisuke Kubo; Saul Ramos-Sanchez; Michael Ratz; Patrick K. S. Vaudrevange, NUCLEAR PHYSICS B, 805, 1-2, 124, 147, Dec. 2008
    English, Technical report
  • Flavor symmetry breaking and vacuum alignment on orbifolds
    Tatsuo Kobayashi; Yuji Omura; Koichi Yoshioka, PHYSICAL REVIEW D, 78, 11, Dec. 2008
    English, Technical report
  • Magnetized orbifold models
    Hiroyuki Abe; Tatsuo Kobayashi; Hiroshi Ohki, Journal of High Energy Physics, 2008, 9, 01 Sep. 2008
    English, Technical report
  • Mirage Mediation of Supersymmetry Breaking and the Higgs Particle
    Kobayashi Tatsuo; Okumura Ken-ichi, Butsuri, 63, 8, 603, 611, 05 Aug. 2008
    Moduli play an important role in low-energy effective theory derived from superstring theory. Their vacuum expectation values provide strength of gauge and Yukawa couplings. Furthermore, their F-components contribute to supersymmetry breaking. Recently, Kachru, Kallosh, Linde and Trivedi prosoed a new type of moduli stabilization mechanism, where all of moduli are stabilized at certain values and the vacuum energy almost vanishes. Furthermore, supersymmetry breaking terms have been studied by Choi, et al. That leads to a unique pattern of soft supersymmetry breaking terms, that is called the mirage mediation. Here we review on the mirage mediation of supersymmetry breaking. In particular, we explain its implication on the fine-tunig problem in the Higgs sector of the minimal supersymmetric standard model., The Physical Society of Japan (JPS), Japanese
  • Mirage Mediation of Supersymmetry Breaking and the Higgs Particle
    KOBAYASHI TATSUO; OKUMURA KEN'ICHI, 日本物理学会誌, 63, 8, 603, 611, 05 Aug. 2008
    Moduli play an important role in low-energy effective theory derived from superstring theory. Their vacuum expectation values provide strength of gauge and Yukawa couplings. Furthermore, their F-components contribute to supersymmetry breaking. Recently, Kachru, Kallosh, Linde and Trivedi prosoed a new type of moduli stabilization mechanism, where all of moduli are stabilized at certain values and the vacuum energy almost vanishes. Furthermore, supersymmetry breaking terms have been studied by Choi, et al. That leads to a unique pattern of soft supersymmetry breaking terms, that is called the mirage mediation. Here we review on the mirage mediation of supersymmetry breaking. In particular, we explain its implication on the fine-tunig problem in the Higgs sector of the minimal supersymmetric standard model., The Physical Society of Japan (JPS), Japanese
  • Soft supersymmetry breaking terms from A4 lepton flavor symmetry
    Hajime Ishimori; Tatsuo Kobayashi; Yuji Omura; Morimitsu Tanimoto, JHEP 0812:082,2008, 29 Jul. 2008
    We study the supersymmetric model with the A4 lepton flavor symmetry, in

    particular soft supersymmetry breaking terms, which are predicted from the A4

    lepton flavor symmetry. We evaluate soft slepton masses and A-terms within the

    framework of supergravity theory. Constraints due to experiments of flavor

    changing neutral current processes are examined., Technical report
  • Nonperturbative moduli superpotential with positive exponents
    Hiroyuki Abe; Tetsutaro Higaki; Tatsuo Kobayashi; Osamu Seto, PHYSICAL REVIEW D, 78, 2, Jul. 2008
    English, Technical report
  • Higher order couplings from heterotic orbifold theory
    Kang-Sin Choi; Tatsuo Kobayashi, NUCLEAR PHYSICS B, 797, 1-2, 295, 321, Jul. 2008
    English, Technical report
  • Soft supersymmetry breaking terms from D(4) x Z(2) lepton flavor symmetry
    Hajime Ishimori; Tatsuo Kobayashi; Hiroshi Ohki; Yuji Omura; Ryo Takahashi; Morimitsu Tanimoto, PHYSICAL REVIEW D, 77, 11, Jun. 2008
    English, Technical report
  • D-4 flavor symmetry for neutrino masses and mixing
    Hajime Ishimoria; Tatsuo Kobayashi; Hiroshi Ohki; Yuji Omura; Ryo Takahashi; Morimitsu Tanimoto, PHYSICS LETTERS B, 662, 2, 178, 184, Apr. 2008
    English, Technical report
  • Dynamically sequestered F-term uplifting in extra dimension
    Hiroyuki Abe; Tetsutaro Higaki; Tatsuo Kobayashi; Yuji Omura, Journal of High Energy Physics, 2008, 4, 01 Apr. 2008
    English, Technical report
  • D4 flavor symmetry in SUSY
    ISHIMORI HAJIME; KOBAYASHI TATSUO; OKI YO; OMURA YUJI; TAKAHASHI RYO; TANIMOTO MORIMITSU, 日本物理学会講演概要集, 63, 1, 10, 10, 29 Feb. 2008
    The Physical Society of Japan (JPS), Japanese
  • Metastable supersymmetry breaking vacua from conformal dynamics
    Hiroyuki Abe; Tatsuo Kobayashi; Yuji Omura, Phys.Rev.D77:065001,2008, 16 Dec. 2007
    We study the scenario that conformal dynamics leads to metastable

    supersymmetry breaking vacua. At a high energy scale, the superpotential is not

    R-symmetric, and has a supersymmetric minimum. However, conformal dynamics

    suppresses several operators along renormalization group flow toward the

    infrared fixed point. Then we can find an approximately R-symmetric

    superpotential, which has a metastable supersymmetry breaking vacuum, and the

    supersymmetric vacuum moves far away from the metastable supersymmetry breaking

    vacuum. We show a 4D simple model. Furthermore, we can construct 5D models with

    the same behavior, because of the AdS/CFT dual., Technical report
  • More about f-term uplifting
    Hiroyuki Abe; Tetsutaro Higaki; Tatsuo Kobayashi, PHYSICAL REVIEW D, 76, 10, Nov. 2007
    English, Book review
  • Discrete R-symmetry anomalies in heterotic orbifold models
    Takeshi Araki; Kang-Sin Choi; Tatsuo Kobayashi; Jisuke Kubo; Hiroshi Ohki, PHYSICAL REVIEW D, 76, 6, Sep. 2007
    English, Book review
  • TeV scale partial mirage unification and neutralino dark matter
    Hiroyuki Abe; Yeong Gyun Kim; Tatsuo Kobayashi; Yasuhiro Shimizu, Journal of High Energy Physics, 2007, 9, 01 Sep. 2007
    English, Technical report
  • String-derived D-4 flavor symmetry and phenomenological implications (vol 76, 035005, 2007)
    Pyungwon Ko; Tatsuo Kobayashi; Jae-hyeon Park; Stuart Raby, PHYSICAL REVIEW D, 76, 5, Sep. 2007
    English, Others
  • R-symmetry, supersymmetry breaking and metastable vacua in global and local supersymmetric theories
    Hiroyuki Abe; Tatsuo Kobayashi; Yuji Omura, JHEP 0711:044,2007, 23 Aug. 2007
    We study N=1 global and local supersymmetric theories with a continuous

    global $U(1)_R$ symmetry as models of dynamical supersymmetry (SUSY) breaking.

    We introduce explicit R-symmetry breaking terms into such models, in particular

    a generalized O'Raifeartaigh model. Such explicit R-symmetry breaking terms can

    lead to a SUSY preserving minimum. We classify explicit R-symmetry breaking

    terms by the structure of newly appeared SUSY stationary points as a

    consequence of the R-breaking effect, which could make the SUSY breaking vacuum

    metastable. We show that the R-breaking terms are basically divided into two

    categories. One of them does not generate a SUSY solution, or yields SUSY

    solutions that disappear in the case of supergravity when we tune a parameter

    so that the original SUSY breaking minimum becomes a Minkowski vacuum. We also

    show that the general argument by Nelson and Seiberg for a dynamical SUSY

    breaking still holds with a local SUSY except for a certain nontrivial case,

    and present concrete examples of the exception., Technical report
  • Relaxed fine-tuning in models with nonuniversal gaugino masses
    Hiroyuki Abe; Tatsuo Kobayashi; Yuji Omura, PHYSICAL REVIEW D, 76, 1, Jul. 2007
    English, Technical report
  • TeV scale mirage mediation and natural little supersymmetric hierarchy
    Kiwoon Choi; Kwang Sik Jeong; Tatsuo Kobayashi; Ken-ichi Okumura, PHYSICAL REVIEW D, 75, 9, May 2007
    English, Book review
  • Stringy origin of non-Abelian discrete flavor symmetries
    Tatsuo Kobayashi; Hans Peter Nilles; Felix Ploeger; Stuart Raby; Michael Ratz, NUCLEAR PHYSICS B, 768, 1-2, 135, 156, Apr. 2007
    English, Technical report
  • Non-factorisable ℤ2 × ℤ2 heterotic orbifold models and Yukawa couplings
    Stefan Förste; Tatsuo Kobayashi; Hiroshi Ohki; Kei-Jiro Takahashi, Journal of High Energy Physics, 2007, 3, 01 Mar. 2007
    English, Technical report
  • Time variation of the proton-electron mass ratio and the fine structure constant with a runaway dilaton
    Takeshi Chiba; Tatsuo Kobayashi; Masahide Yamaguchi; Jun'ichi Yokoyama, PHYSICAL REVIEW D, 75, 4, Feb. 2007
    English, Technical report
  • Moduli stabilization, F-term uplifting, and soft supersymmetry breaking terms
    Hiroyuki Abe; Tetsutaro Higaki; Tatsuo Kobayashi; Yuji Omura, PHYSICAL REVIEW D, 75, 2, Jan. 2007
    English, Technical report
  • Dynamical realization of democratic Yukawa matrices and alignment of A terms
    Tatsuo Kobayashi; Yuji Omura; Haruhiko Terao, PHYSICAL REVIEW D, 74, 5, Sep. 2006
    English, Technical report
  • Fine-tuning in gauge mediated supersymmetry breaking models and induced top Yukawa coupling
    Tatsuo Kobayashi; Haruhiko Terao; Akito Tsuchiya, PHYSICAL REVIEW D, 74, 1, Jul. 2006
    English, Technical report
  • Moduli-mixing racetrack model
    H Abe; T Higaki; T Kobayashi, NUCLEAR PHYSICS B, 742, 187, 207, May 2006
    English, Technical report
  • 29pXA-6 An attempt to solve fine tuning problem in Susy standart model
    kobayashi Tatsuo; Terao Haruhiko; Tsuchiya Akito, Meeting abstracts of the Physical Society of Japan, 61, 1, 10, 10, 04 Mar. 2006
    The Physical Society of Japan (JPS), Japanese
  • Little SUSY hierarchy in mixed modulus-anomaly mediation
    K Choi; KS Jeong; T Kobayashi; K Okumura, PHYSICS LETTERS B, 633, 2-3, 355, 361, Feb. 2006
    English, Technical report
  • Kachru-Kallosh-Linde-Trivedi-type models with moduli-mixing superpotential
    H Abe; T Higaki; T Kobayashi, PHYSICAL REVIEW D, 73, 4, Feb. 2006
    English, Technical report
  • Remark on integrating out heavy moduli in flux compactification
    Hiroyuki Abe; Tetsutaro Higaki; Tatsuo Kobayashi, Physical Review D - Particles, Fields, Gravitation and Cosmology, 74, 4, 2006
    English, Technical report
  • More about soft terms and FCNC in realistic string constructions
    Tatsuo Kobayashi; Carlos Mũoz, Journal of High Energy Physics, 1, 1107, 1117, 2006
    English, Technical report
  • Flavor structure and coupling selection rule from intersecting D-branes
    T Higaki; N Kitazawa; T Kobayashi; K Takahashi, PHYSICAL REVIEW D, 72, 8, Oct. 2005
    English, Technical report
  • Induced top-Yukawa coupling and suppressed Higgs mass parameters
    T Kobayashi; H Nakano; H Terao, PHYSICAL REVIEW D, 71, 11, Jun. 2005
    English, Technical report
  • Democratic mass matrices induced by strong gauge dynamics and large mixing angles for leptons
    Tatsuo Kobayashi; Hiroaki Shirano; Haruhiko Terao, Progress of Theoretical Physics, 113, 5, 1077, 1099, May 2005
    English, Technical report
  • Lepton masses and mixing angles from heterotic orbifold models
    P Ko; T Kobayashi; JH Park, PHYSICAL REVIEW D, 71, 9, May 2005
    English, Technical report
  • Yukawa coupling structure in intersecting D-brane models
    N Kitazawa; T Kobayashi; N Maru; N Okada, EUROPEAN PHYSICAL JOURNAL C, 40, 4, 579, 587, Apr. 2005
    English, Technical report
  • Large mass scale by strong gauge dynamics with infrared fixed point
    Tatsuo Kobayashi; Hiroaki Nakano; Haruhiko Terao; Yoshihisa Yamada, Progress of Theoretical Physics, 113, 2, 413, 427, Feb. 2005
    English, Technical report
  • 素粒子物理学の進展 強統一とレプトン混合角による民主的質量行列
    寺尾治彦; 小林達夫; 白野宏昌, 素粒子論研究, 110, 4, D7-D8, D8, 20 Jan. 2005
    Soryushiron Kenkyu Editorial Office, Japanese
  • Searching for realistic 4d string models with a Pati-Salam symmetry. Orbifold grand unified theories from heterotic string compactification on a Z(6) orbifold
    T Kobayashi; S Raby; RJ Zhang, NUCLEAR PHYSICS B, 704, 1-2, 3, 55, Jan. 2005
    English, Book review
  • Radiative stabilization of warped space
    Tatsuo Kobayashi; Koichi Yoshioka, JHEP 0411:024,2004, 30 Sep. 2004
    Higher-dimensional field theory has been applied to explore various issues in

    recent particle physics such as the gauge hierarchy problem. In order for such

    approaches to be viable, a crucial ingredient is to fix the sizes of extra

    dimensions at some finite values, which sizes are generically free parameters

    in the theory. In this paper, we present several schemes to determine the

    radius of extra dimension in warped five-dimensional theory. In every case, a

    non-vanishing Fayet-Iliopoulos term for abelian gauge factor plays a crucial

    role for the radius stabilization. It is radiatively generated in the presence

    of charged matter fields and the compactification is therefore spontaneous, not

    forced by selected operators. The low-energy supersymmetry is broken or

    unbroken, and the radius can be fixed to give a small or large scale hierarchy

    without any fine tuning of parameters. We also discuss a model of the radius

    stabilization correlated with Yukawa hierarchy and supersymmetry breaking., Technical report
  • Quark masses and mixing angles in heterotic orbifold models
    P Ko; T Kobayashi; JH Park, PHYSICS LETTERS B, 598, 3-4, 263, 272, Sep. 2004
    English, Technical report
  • Constructing 5d orbifold grand unified theories from heterotic strings
    T Kobayashi; S Raby; RJ Zhang, PHYSICS LETTERS B, 593, 262, 270, Jul. 2004
    English, Technical report
  • Supersymmetry breaking in warped geometry
    K Choi; DY Kim; IW Kim; T Kobayashi, EUROPEAN PHYSICAL JOURNAL C, 35, 2, 267, 275, Jun. 2004
    English, Technical report
  • Anomalous U(1) D-term contribution in type I string models
    T Higaki; Y Kawamura; T Kobayashi; H Nakano, PHYSICAL REVIEW D, 69, 8, Apr. 2004
    English, Technical report
  • Suppressed supersymmetry breaking terms in the Higgs sector
    Tatsuo Kobayashi; Haruhiko Terao, JHEP 0407 (2004) 026, 31 Mar. 2004
    We study the little hierarchy between mass parameters in the Higgs sector and

    other SUSY breaking masses. This type of spectrum can relieve the fine-tuning

    problem in the MSSM Higgs sector. Our scenario can be realized by

    superconformal dynamics. The spectrum in our scenario has significant

    implications in other phenomenological aspects like the relic abundance of the

    lightest neutralino and relaxation of the unbounded-from-below constraints., Technical report
  • Non-perturbative Kähler potential, dilaton stabilization and Fayet-Iliopoulos term
    Tetsutaro Higaki; Yoshiharu Kawamura; Tatsuo Kobayashi; Hiroaki Nakano, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 582, 3-4, 257, 262, 04 Mar. 2004
    Elsevier, English, Technical report
  • D-term Inflation and Nonperturbative Kahler Potential of Dilaton
    Tetsutaro Higaki; Tatsuo Kobayashi; Osamu Seto, JHEP 0407 (2004) 035, 19 Feb. 2004
    We study the $D$-term inflation scenario with a nonperturbative K\"ahler

    potential of the dilaton field. Although the FI term which leads an

    inflationary expansion is given by the derivative of the K\"ahler potential

    with respect to the dilaton in heterotic string models with anomalous U(1), the

    too large magnitude is problematic for a viable $D$-term inflation. In this

    paper, we point out that the K\"ahler potential with a nonperturbative term can

    reduce the magnitude of FI term to desired values while both the dilaton

    stabilization and $D$-term domination in the potential are realized by

    nonperturbative superpotential., Technical report
  • Localization of heterotic anomalies on various hypersurfaces of T-6/Z(4)
    SG Nibbelink; M Hillenbach; T Kobayashi; MGA Walter, PHYSICAL REVIEW D, 69, 4, Feb. 2004
    English, Technical report
  • Heterotic Yukawa couplings and Wilson lines
    O Lebedev, STRING PHENOMENOLOGY 2003, 256, 259, 2004
    English, Technical report
  • Dilaton and moduli fields in D-term inflation
    T Kobayashi; O Seto, PHYSICAL REVIEW D, 69, 2, Jan. 2004
    English, Technical report
  • Exact S3 symmetry solving the supersymmetric flavor problem
    Tatsuo Kobayashi; Jisuke Kubo; Haruhiko Terao, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 568, 1-2, 83, 91, 21 Aug. 2003
    Elsevier, English, Technical report
  • Twisted moduli stabilization in type I string models
    T Higaki; T Kobayashi, PHYSICAL REVIEW D, 68, 4, 046006, Aug. 2003
    English
  • Exact S-3 symmetry solving the supersymmetric flavor problem
    T Kobayashi; J Kubo; H Terao, PHYSICS LETTERS B, 568, 1-2, 83, 91, Aug. 2003
    English
  • Flavor violation in supersymmetric theories with gauged flavor symmetries
    T Kobayashi; H Nakano; H Terao; K Yoshioka, PROGRESS OF THEORETICAL PHYSICS, 110, 2, 247, 267, Aug. 2003
    English, Book review
  • Heterotic string backgrounds and CP violation
    T Kobayashi; O Lebedev, PHYSICS LETTERS B, 565, 1-4, 193, 200, Jul. 2003
    English
  • Heterotic Yukawa couplings and continuous Wilson lines
    T Kobayashi; O Lebedev, PHYSICS LETTERS B, 566, 1-2, 164, 170, Jul. 2003
    English
  • Four-dimensional construction of bulk supersymmetry breaking
    T Kobayashi; N Maru; K Yoshioka, EUROPEAN PHYSICAL JOURNAL C, 29, 2, 277, 284, Jul. 2003
    English, Technical report
  • Heterotic string backgrounds and CP violation
    Tatsuo Kobayashi; Oleg Lebedev, Phys.Lett. B565 (2003) 193-200, 25 Apr. 2003
    In the framework of $Z_N$ orbifolds, we discuss effects of heterotic string

    backgrounds including discrete Wilson lines on the Yukawa matrices and their

    connection to CP violation., Technical report
  • Finite theories and the supersymmetry flavor problem
    KS Babu; T Kobayashi; J Kubo, PHYSICAL REVIEW D, 67, 7, 075018, Apr. 2003
    English, Book review
  • Yukawa hierarchy transfer based on superconformal dynamics and geometrical realization in string models
    T Kobayashi; H Nakano; T Noguchi; H Terao, JOURNAL OF HIGH ENERGY PHYSICS, 0302, 2, 022, Feb. 2003
    English
  • Field localization in warped gauge theories
    H Abe; T Kobayashi; N Maru; K Yoshioka, PHYSICAL REVIEW D, 67, 4, 045019, Feb. 2003
    English
  • Field localization in warped gauge theories
    H Abe; T Kobayashi; N Maru; K Yoshioka, PHYSICAL REVIEW D, 67, 4, Feb. 2003
    English, Technical report
  • SUSY Flavor Problem and Warped Geometry
    Kiwoon Choi; Do Young Kim; Ian-Woo Kim; Tatsuo Kobayashi, 18 Jan. 2003
    We point out that supersymmetric warped geometry can provide a solution to

    the SUSY flavor problem, while generating hierarchical Yukawa couplings. In

    supersymmetric theories in a slice of AdS_5 with the Kaluza-Klein scale M_KK

    much higher than the weak scale, if all visible fields originate from 5D bulk

    fields and supersymmetry breaking is mediated by the bulk radion superfield

    and/or some brane chiral superfields, potentially dangerous soft scalar masses

    and trilinear $A$ parameters at M_KK can be naturally suppressed compared to

    the gaugino masses by small warp factor. We present simple models yielding

    phenomenologically interesting patterns of soft parameters in this framework., Technical report
  • Wave-function profile and SUSY breaking in 5D model with Fayet-Iliopoulos terms
    Hiroyuki Abe; Tetsutaro Higaki; Tatsuo Kobayashi, Progress of Theoretical Physics, 109, 5, 809, 830, 2003
    Yukawa Institute for Theoretical Physics, English
  • Flavor Violation in Supersymmetric Theories with Gauged Flavor Symmetries
    Tatsuo Kobayashi; Hiroaki Nakano; Haruhiko Terao; Koichi Yoshioka, Progress of Theoretical Physics, 110, 2, 247, 267, 2003
    Yukawa Institute for Theoretical Physics, English, Technical report
  • Wave-function profile and SUSY breaking in 5D model with Fayet-Iliopoulos terms
    Hiroyuki Abe; Tetsutaro Higaki; Tatsuo Kobayashi, Progress of Theoretical Physics, 109, 5, 809, 830, 2003
    Yukawa Institute for Theoretical Physics, English, Technical report
  • Twisted moduli stabilization in type I string models
    Tetsutaro Higaki; Tatsuo Kobayashi, Physical Review D, 68, 4, 2003
    English, Technical report
  • Sfermion mass degeneracy, superconformal dynamics, and supersymmetric grand unified theories
    T Kobayashi; H Nakano; T Noguchi; H Terao, PHYSICAL REVIEW D, 66, 9, 095011, Nov. 2002
    English
  • Sfermion mass degeneracy, superconformal dynamics, and supersymmetric grand unified theories
    T Kobayashi; H Nakano; T Noguchi; H Terao, PHYSICAL REVIEW D, 66, 9, Nov. 2002
    English, Technical report
  • Yukawa Hierarchy Transfer Based on Superconformal Dynamics and Geometrical Realization in String Models
    Tatsuo Kobayashi; Hiroaki Nakano; Tatsuya Noguchi; Haruhiko Terao, JHEP 0302:022,2003, 08 May 2002
    We propose a scenario that leads to hierarchical Yukawa couplings and

    degenerate sfermion masses at the same time, in the context of

    extra-dimensional models, which can be naturally embedded in a wide class of

    string models. The hierarchy of Yukawa couplings and degeneracy of sfermion

    masses can be realized thanks to superconformal gauge dynamics. The sfermion

    mass degeneracy is guaranteed by taking the superconformal fixed point to be

    family independent. In our scenario, the origin of Yukawa hierarchy is

    attributed to geometry of compactified dimensions and the consequent volume

    dependence of gauge couplings in the superconformal sectors. The difference in

    these gauge couplings is dynamically transferred to the hierarchy of the Yukawa

    couplings. Thus, our scenario combines a new dynamical approach and the

    conventional geometrical approach to the supersymmetric flavor problem., Technical report
  • More about Kaluza-Klein regularization
    Tatsuo Kobayashi; Haruhiko Terao, Progress of Theoretical Physics, 107, 4, 785, 792, Apr. 2002
    English, Technical report
  • Yukawa hierarchy transfer from the superconformal sector and degenerate sfermion masses - art. no. 015004
    T Kobayashi; H Nakano; H Terao, PHYSICAL REVIEW D, 65, 1, 015006, Jan. 2002
    English
  • Yukawa hierarchy transfer from the superconformal sector and degenerate sfermion masses - art. no. 015004
    T Kobayashi; H Nakano; H Terao, PHYSICAL REVIEW D, 65, 1, Jan. 2002
    English, Technical report
  • Phenomenological Implications of Models with Extra Dimensions
    Kobayashi Tatsuo, Soryushiron Kenkyu, 103, 6, F43, F46, 20 Sep. 2001
    Soryushiron Kenkyu, English
  • Direct detection of neutralino dark matter and the anomalons dipole moment of the muon
    M Drees; YG Kim; T Kobayashi; MM Nojiri, PHYSICAL REVIEW D, 63, 11, 115009, Jun. 2001
    English
  • Fermion mass hierarchies and small mixing angles from extra dimensions
    M Bando; T Kobayashi; T Noguchi; K Yoshioka, PHYSICAL REVIEW D, 63, 11, 113017, Jun. 2001
    English
  • Can we distinguish SUSY breaking terms between weakly and strongly coupled heterotic string theories?
    Tatsuo Kobayashi, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 506, 1-2, 187, 192, 03 May 2001
    English, Technical report
  • Restricted flavor structure of soft SUSY breaking trilinear couplings
    T Kobayashi; O Vives, PHYSICS LETTERS B, 506, 3-4, 323, 330, May 2001
    English
  • 29pSJ-3 SUSY breaking mediation in extra dimensions
    Kobayashi Tatsuo, Meeting abstracts of the Physical Society of Japan, 56, 1, 7, 7, 09 Mar. 2001
    The Physical Society of Japan (JPS), Japanese
  • Sfermion masses in Nelson-Strassler-Type models : SUSY standard models coupled with SCFTs(??)
    Phys. Rev., D64, 075003, 2001
  • Direct detection of neutralino dark matter and the anomalous dipole moment of the muon
    Manuel Drees; Yeong Gyun Kirn; Tatsuo Kobayashi; Mihoko M. Nojiri, Physical Review D, 63, 11, 2001
    English, Technical report
  • Fermion mass hierarchies and small mixing angles from extra dimensions
    Masako Bando; Tatsuo Kobayashi; Tatsuya Noguchi; Koichi Yoshioka, Physical Review D, 63, 11, 2001
    English, Technical report
  • Sfermion masses in Nelson-Strassler-type models: Supersymmetric standard models coupled with superconformal field theories
    Tatsuo Kobayashi; Haruhiko Terao, Physical Review D, 64, 7, 2001
    English, Technical report
  • Kaluza-Klein mediated supersymmetry breaking
    T Kobayashi; K Yoshioka, PHYSICAL REVIEW LETTERS, 85, 26, 5527, 5530, Dec. 2000
    English
  • Softly broken supersymmetric Gauge-Higgs-Yukawa theories as renormalizable composite models
    Tatsuo Kobayashi; Haruhiko Terao, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 489, 1-2, 233, 242, 14 Sep. 2000
    English
  • Kaluza-Klein Mediated Supersymmetry Breaking
    Tatsuo Kobayashi; Koichi Yoshioka, Phys.Rev.Lett. 85 (2000) 5527-5530, 08 Aug. 2000
    We discuss a framework for communicating supersymmetry breaking to the

    visible sector where the radius modulus, which determines the size of extra

    dimensions, has an auxiliary vacuum expectation value. The modulus couplings

    generate mass splitting in Kaluza-Klein supermultiplets and they act as

    messengers of supersymmetry breaking. The soft masses are expressed in terms of

    renormalization-group functions and the sparticle spectrum is determined by

    what kind of field propagates in the bulk. This framework also provides new

    possibilities for solving the supersymmetric flavor problem., Technical report
  • New RG-invariants of soft supersymmetry breaking parameters
    Tatsuo Kobayashi; Koichi Yoshioka, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 486, 1-2, 223, 227, 27 Jul. 2000
    English, Technical report
  • EDM-free supersymmetric CP violation with non-universal soft terms
    S Khalil; T Kobayashi; O Vives, NUCLEAR PHYSICS B, 580, 1-2, 275, 288, Jul. 2000
    English
  • Electroweak symmetry breaking and s-spectrum in M-theory
    T Kobayashi; J Kubo; H Shimabukuro, NUCLEAR PHYSICS B, 580, 1-2, 3, 28, Jul. 2000
    English
  • Softly Broken Supersymmetric Gauge-Higgs-Yukawa Theories as Renormalizable Composite Models
    Tatsuo Kobayashi; Haruhiko Terao, Phys.Lett. B489 (2000) 233-242, 26 May 2000
    We examine the (softly broken) supersymmetric gauge-Higgs-Yukawa theories

    satisfying the compositeness conditions at a certain scale. In these theories

    the Higgs superfields can be regarded as the chiral composite fields. It is

    found that there are the fundamental theories, which contain the dimension 5

    interactions and the hard SUSY breaking in perturbation, turn to be

    renormalizable and also softly broken theories in the nonperturbative

    framework. The soft SUSY breaking parameters as well as the Yukawa coupling in

    the corresponding gauge-Higgs-Yukawa theories are restricted by the

    renormalization group invariant relations., Technical report
  • RG-invariant Sum Rule in Anomaly Mediated SUSY Breaking
    KOBAYASHI TATSUO, Soryushiron Kenkyu, 101, 2, B25, B26, 20 May 2000
    Soryushiron Kenkyu, English
  • Yukawa hierarchy from extra dimensions and infrared fixed points
    Masako Bando; Tatsuo Kobayashi; Tatsuya Noguchi; Koichi Yoshioka, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 480, 1-2, 187, 192, 04 May 2000
    English, Technical report
  • Yukawa hierarchy from extra dimensions and infrared fixed points
    M Bando; T Kobayashi; T Noguchi; K Yoshioka, PHYSICS LETTERS B, 480, 1-2, 187, 192, May 2000
    English
  • RG-invariant Sum Rule in a Generalization of Anomaly Mediated SUSY Breaking Models
    Marcela Carena; Katri Huitu; Tatsuo Kobayashi, Nucl.Phys.B592:164-182,2001, 20 Mar. 2000
    We study a generalization of anomaly-mediated supersymmetry breaking (AMSB)

    scenarios, under the assumption that the effects of the high-scale theory do

    not completely decouple and D-term type contributions can be therefore present.

    We investigate the effect of such possible D-term additional contributions to

    soft scalar masses by requiring that, for non-vanishing, renormalizable Yukawa

    couplings $Y^{ijk} $, the sum of squared soft supersymmetry breaking mass

    parameters, $M^2_{ijk} \equiv m_i^2+m_j^2+m_k^2$, is RG-invariant, in the sense

    that it becomes independent of the specific ultraviolet boundary conditions as

    it occurs in the AMSB models. These type of models can avoid the problem of

    tachyonic solutions for the slepton mass spectrum present in AMSB scenarios. We

    implement the electroweak symmetry breaking condition and explore the sparticle

    spectrum associated with this framework. To show the possible diversity of the

    sparticle spectrum, we consider two examples, one in which the D-terms induce a

    common soft supersymmetry breaking mass term for all sfermion masses, and

    another one in which a light stop can be present in the spectrum., Technical report
  • EDM-free supersymmetric CP violation with non-universal soft terms
    Shaaban Khalil; Tatsuo Kobayashi; Oscar Vives, Nucl.Phys. B580 (2000) 275-288, 10 Mar. 2000
    Non-universality in the soft breaking terms is a common feature in most

    superstring inspired SUSY models. This property is required to obtain sizeable

    CP violation effects from SUSY and, on the other hand, can be used to avoid the

    Electric Dipole Moment constraints. We take advantage of these qualities and

    explore a class of SUSY models based on type I string theory where scalar

    masses, gaugino masses and trilinear couplings are non-universal. In this

    framework, we show that, in the presence of large SUSY phases, the bounds on

    the Electric Dipole Moments can be controled without fine-tuning. At the same

    time, we find that these phases, free from EDM constraints, lead to large

    contributions to the observed CP phenomena in Kaon system and, in particular,

    to direct CP violation in epsilon'/epsilon., Technical report
  • Phenomenological constraints on SUSYSU(5) GUTs with nonuniversal gaugino masses
    K Huitu; Y Kawamura; T Kobayashi; K Puolamaki, PHYSICAL REVIEW D, 61, 3, 035001, Feb. 2000
    English
  • "RG-invariant Sum Rule in a Generalization of Anomaly-Mediated SUSY Breaking Models"(jointly worked)
    Nucl. Phys., B592, 164, 182, 2000
  • "Infrared alignment of SUSY flavor structures"(jointly worked)
    Phys. Rev., D62, 115003, 2000
  • Bottom-up approach to B-parameter in minimal supersymmetric standard model
    Y Kawamura; T Kobayashi; M Watanabe, INTERNATIONAL JOURNAL OF MODERN PHYSICS A, 15, 1, 81, 103, Jan. 2000
    English
  • Phenomenological constraints on SUSYSU(5) GUTs with non-universal gaugino masses
    K Huitu; Y Kawamura; T Kobayashi; K Puolamaki, HIGH ENERGY PHYSICS 99, PROCEEDINGS, 786, 788, 2000
    English, Technical report
  • Infrared alignment of supersymmetric flavor structures
    Tatsuo Kobayashi, Physical Review D - Particles, Fields, Gravitation and Cosmology, 62, 11, 8, 2000
    English, Technical report
  • Generic gravitational corrections to gauge couplings in SUSYSU(5) GUTs
    K Huitu; Y Kawamura; T Kobayashi; K Puolamaki, PHYSICS LETTERS B, 468, 1-2, 111, 117, Nov. 1999
    English
  • F-term inflation in M-theory with five-branes
    SM Harun-or-Rashid; T Kobayashi; H Shimabukuro, PHYSICS LETTERS B, 466, 2-4, 95, 99, Nov. 1999
    English
  • CP violation in a supersymmetric model with nondegenerate A terms
    S Khalil; T Kobayashi; A Masiero, PHYSICAL REVIEW D, 60, 7, 075003, Oct. 1999
    English
  • Generic Gravitational Corrections to Gauge Couplings in SUSY SU(5) GUTs
    Katri Huitu; Yoshiharu Kawamura; Tatsuo Kobayashi; Kai Puolamaki, Phys.Lett. B468 (1999) 111-117, 02 Sep. 1999
    We study non-universal corrections to the gauge couplings due to higher

    dimensional operators in supersymmetric SU(5) grand unified theories. The

    corrections are, in general, parametrized by three components originating from

    {\bf 24}, {\bf 75} and {\bf 200} representations. We consider the prediction of

    $\alpha_3(M_Z)$ along each {\bf 24}, {\bf 75} and {\bf 200} direction, and

    their linear combinations. The magnitude of GUT scale and its effects on proton

    decay are discussed. Non-SUSY case is also examined., Technical report
  • Gauge Coupling Unification with Extra Dimensions and Correction due to Higher Dimensional Operators
    Katri Huitu; Tatsuo Kobayashi, Phys.Lett. B470 (1999) 90-94, 470, 1/4, 90, 94, 21 Jun. 1999
    We study the gauge coupling unification with extra dimensions. We take into

    account corrections due to the higher dimensional operators. We show the

    prediction of $\alpha_3(M_Z)$ is sensitive to such corrections, even if

    $c<\Phi>/M=O(0.01)$. We also discuss the $b-\tau$ Yukawa unification., Technical report
  • Supersymmetric CP violation $ε'/ε$ due to asymmetric A-matrix
    Shaaban Khalil; Tatsuo Kobayashi, Phys.Lett.B460:341-347,1999, B460, 341, 347, 16 Jun. 1999
    We study contributions of supersymmetric CP phases to the CP violation

    $\epsilon'/\epsilon$ in models with asymmetric $A$-matrices. We consider

    asymmetric $A$-matrices, which are obtained from string-inspired supergravity.

    We show that a certain type of asymmetry of $A$-matrices enhances

    supersymmetric contributions to the CP violation $\epsilon'/\epsilon$ and the

    supersymmetric contribution to $\epsilon'/\epsilon$ can be of order of the KTeV

    result, $\epsilon'/\epsilon \sim 10^{-3}$., Technical report
  • Running of soft parameters in extra space-time dimensions
    Tatsuo Kobayashi; Jisuke Kubo; Myriam Mondragón; George Zoupanos, Nuclear Physics B, 550, 1-2, 99, 122, 14 Jun. 1999
    Elsevier, English, Technical report
  • Running of soft parameters in extra space-time dimensions
    T Kobayashi; J Kubo; M Mondragon; G Zoupanos, NUCLEAR PHYSICS B, 550, 1-2, 99, 122, Jun. 1999
    English
  • Electroweak symmetry breaking and s-spectrum in M-theory
    Tatsuo Kobayashi; Jisuke Kubo; Hitoshi Shimabukuro, Nucl.Phys. B580 (2000) 3-28, 01 Apr. 1999
    We study soft SUSY breaking parameters in M-theory with and without 5-brane

    moduli fields. We investigate successful electroweak symmetry breaking and the

    positivity of stau mass squared. We study mass spectra in allowed regions., Technical report
  • CP violation in supersymmetric model with non-degenerate A-terms
    Shaaban Khalil; Tatsuo Kobayashi; Antonio Masiero, Phys.Rev. D60 (1999) 075003, 01 Apr. 1999
    We study the CP phases of the soft supersymmetry breaking terms in

    string-inspired models with non-universal trilinear couplings. We show that

    such non-universality plays an important role on all CP violating processes. In

    particular these new supersymmetric sources of CP violation may significantly

    contribute to the observed CP phenomena in kaon physics while respecting the

    severe bound on the electric dipole moment of the neutron., Technical report
  • On Different Criteria for Confinement
    Masud Chaichian; Tatsuo Kobayashi, Phys.Lett. B481 (2000) 26-32, 481, 1, 26, 32, 12 Mar. 1999
    We compare two approaches in supersymmetric confinement, the Seiberg

    formulation and the superconvergence rule. For the latter, the critical point

    is $\gamma_{00}=0$ in the Landau gauge. We find $4\gamma_{00}=\beta_0$ is the

    critical point for most of confining theories without a tree-level

    superpotential in the Seiberg formulation, in particular, in the large $N_c$

    and $N_f$ limit. We show how confining theories with a discrete symmetry and a

    tree-level superpotential connect these two critical points: the large and

    small discrete symmetry limits correspond to the critical points

    $4\gamma_{00}=\beta_0$ and $\gamma_{00}=0$, respectively., Technical report
  • F-term inflation in M-theory with five-branes
    S. M. Harun-or-Rashid; Tatsuo Kobayashi; Hitoshi Shimabukuro, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 466, 2-4, 95, 99, 1999
    Elsevier, English, Technical report
  • Constraints on finite soft supersymmetry breaking terms
    T Kobayashi; J Kubo; M Mondragon; G Zoupanos, INTERNATIONAL EUROPHYSICS CONFERENCE ON HIGH ENERGY PHYSICS, 877, 882, 1999
    English, Technical report
  • Electroweak radiative breaking in low energy effective theory of M-theory.
    KUBO JISUKE; KOBAYASHI TATSUO; SHIMABUKURO HITOSHI, 日本物理学会北陸支部・応用物理学会北陸・信越支部合同講演会講演予稿集, 1998, 17, Dec. 1998
    Japanese
  • Infrared behaviour of softly broken SQCD and its dual
    A Karch; T Kobayashi; J Kubo; G Zoupanos, PHYSICS LETTERS B, 441, 1-4, 235, 242, Nov. 1998
    English
  • Constraints on supersymmetric SO(10) GUTs with sum rules among soft masses
    Y Kawamura; T Kobayashi; H Shimabukuro, PHYSICS LETTERS B, 436, 1-2, 108, 116, Sep. 1998
    English
  • Infrared Behaviour of Softly Broken SQCD and Its Dual
    Andreas Karch; Tatsuo Kobayashi; Jisuke Kubo; George Zoupanos, Phys.Lett. B441 (1998) 235-242, 29 Aug. 1998
    Applying the recently obtained results on the renormalization of soft

    supersymmetry-breaking parameters, we investigate the infrared behaviour of the

    softly broken supersymmetric QCD as well as its dual theory in the conformal

    window. Under general assumptions on $\beta$-functions, it is shown that the

    soft supersymmetry-breaking parameters asymptotically vanish in the infrared

    limit so that superconformal symmetry in softly broken supersymmetric QCD and

    in its dual theory revives at the infrared fixed point, provided the soft

    scalar masses satisfy certain renormalization group invariant relations. If

    these relations are not satisfied, there exist marginal operators in both

    theories that lead to the breaking of supersymmetry and also colour symmetry., Technical report
  • Yukawa unification in moduli-dominant SUSY breaking
    Shaaban Khalil; Tatsuo Kobayashi, Nuclear Physics B, 526, 1-3, 99, 114, 24 Aug. 1998
    Elsevier, English, Technical report
  • Vacuum Structure of Softly Broken N=1 Supersymmetric QCD
    Masud Chaichian; Tatsuo Kobayashi, Phys.Lett. B442 (1998) 192-198, 19 Aug. 1998
    We study softly broken N=1 supersymmetric QCD with the gauge group $SU(N_c)$

    and $N_f$ flavors of quark pairs. We investigate vacuum structure of the theory

    with generic soft supersymmetry breaking terms. Trilinear soft breaking terms

    play an essential role in determining vacua. For $N_f=N_c+1$, chiral symmetry

    is broken for a sufficiently large magnitude of trilinear couplings, while it

    is unbroken in the case with only soft masses. In the case where appearance of

    trilinear coupling terms is allowed, i.e. for $N_f \geq N_c+1$, we have two

    possible vacua, the trivial and non-trivial ones. Otherwise, we only have the

    non-trivial vacuum, which corresponds to the non-trivial vacuum in the $N_f

    \geq N_c+1$ theory., Technical report
  • Yukawa unification in moduli-dominant SUSY breaking
    S Khalil; T Kobayashi, NUCLEAR PHYSICS B, 526, 1-3, 99, 114, Aug. 1998
    English
  • Quark Mass Matrices in String Models
    KOBAYASHI TATSUO, Soryushiron Kenkyu, 97, 4, D31, D33, 20 Jul. 1998
    Soryushiron Kenkyu, English
  • Softly broken N = 1 supersymmetric QCD
    M Chaichian; WF Chen; T Kobayashi, PHYSICS LETTERS B, 432, 1-2, 120, 127, Jul. 1998
    English
  • Sum rules in the superpartner spectrum of the minimal supersymmetric standard model
    Y Kawamura; T Kobayashi; J Kubo, PHYSICS LETTERS B, 432, 1-2, 108, 113, Jul. 1998
    English
  • Constraints on Supersymmetric SO(10) GUTs with Sum Rules among Soft Masses
    Yoshiharu Kawamura; Tatsuo Kobayashi; Hitoshi Shimabukuro, Phys.Lett.B436:108-116,1998, 15 May 1998
    We study phenomenological aspects of supersymmetric SO(10) GUTs with sum

    rules among soft SUSY breaking parameters. In particular, the sum rule related

    to the stau mass leads to the constraints from the requirements of successful

    electroweak breaking and the positivity of stau mass squared. The bottom quark

    mass is also estimated., Technical report
  • Further all-loop results in softly-broken supersymmetric gauge theories
    T Kobayashi; J Kubo; G Zoupanos, PHYSICS LETTERS B, 427, 3-4, 291, 299, May 1998
    English
  • Softly Broken N=1 Supersymmetric QCD
    Masud Chaichian; Wen-Feng Chen; Tatsuo Kobayashi, Phys.Lett. B432 (1998) 120-127, 18 Mar. 1998
    We study softly broken N=1 supersymmetric QCD with the gauge group $SU(N_c)$

    and $N_f$ flavours of quarks for $N_f > N_c+1$. We investigate the phase

    structure of its dual theory adding generic soft supersymmetry breking terms,

    i.e. soft scalar masses, trilinear coupling terms of scalar fields and gaugino

    masses. It is found that the trilinear coupling terms play an improtant role in

    determining the potential minima. Also we compare softly broken original and

    dual theories in the broken phase., Technical report
  • Bottom-up approach to B-parameter in minimal supersymmetric standard model
    Yoshiharu Kawamura; Tatsuo Kobayashi; Manabu Watanabe, Int.J.Mod.Phys. A15 (2000) 81-104, 16 Feb. 1998
    We study $\mu$ and $B$-parameters in the minimal supersymmetric standard

    model (MSSM) based on the radiative electroweak symmetry breaking scenario

    using $\lq\lq$bottom-up" approach and show how useful our approach is to select

    a phenomenologically viable model beyond the MSSM under the assumption that the

    underlying theory is a string model or a gauge-Yukawa unified gauge model., Technical report
  • Probing μ-term generation mechanism in string models
    Yoshiharu Kawamura; Tatsuo Kobayashi; Manabu Watanabe, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 419, 1-4, 157, 166, 11 Feb. 1998
    Elsevier, English, Technical report
  • Further all-loop results in softly-broken supersymmetric gauge theories
    Tatsuo Kobayashi; Jisuke Kubo; George Zoupanos, Phys.Lett.B427:291-299,1998, 07 Feb. 1998
    It is proven that the recently found, renormalization-group invariant sum

    rule for the soft scalar masses in softly-broken N=1 supersymmetric

    gauge-Yukawa unified theories can be extended to all orders in perturbation

    theory. In the case of finite unified theories, the sum rule ensures the

    all-loop finiteness in the soft supersymmetry breaking sector. As a byproduct

    the exact $\beta$ function for the soft scalar masses in the

    Novikov-Shifman-Vainstein-Zakharov (NSVZ) scheme for softly-broken

    supersymmetric QCD is obtained. It is also found that the singularity appearing

    in the sum rule in the NSVZ scheme exactly coincides with that which has been

    previously found in a certain class of superstring models in which the massive

    string states are organized into $N = 4$ supermultiplets., Technical report
  • Constraints on finite soft supersymmetry-breaking terms
    T Kobayashi; J Kubo; M Mondragon; G Zoupanos, NUCLEAR PHYSICS B, 511, 1-2, 45, 68, Feb. 1998
    English, Book review
  • "Vacuum Structure of Softly Broken N=1 Supersymmetric QCD"(jointly worked)
    Phys. Lett., 442, 1/4, 192, 198, 1998
  • "Quark Mass Matrices in Superstring Models"(jointly worked)
    Int. J. Mod. Phys., 13, 13, 2201, 2215, 1998
  • Notes on Curtright-Zachos deformations of osp(1,2) and super Virasoro algebras
    N Aizawa; T Kobayashi; HT Sato, INTERNATIONAL JOURNAL OF MODERN PHYSICS A, 12, 32, 5867, 5883, Dec. 1997
    English
  • Sum rule of soft mass parameter in SO(10) type SUSYGUT model and its permited region.
    KUBO HARUSUKE; KOBAYASHI TATSUO; SHIMABUKURO HITOSHI, 日本物理学会北陸支部・応用物理学会北陸・信越支部合同講演会講演予稿集, 1997, 146, Dec. 1997
    Japanese
  • Sum rules in the superpartner spectrum of the minimal supersymmetric standard model
    Yoshiharu Kawamura; Tatsuo Kobayashi; Jisuke Kubo, Phys.Lett. B432 (1998) 108-113, 24 Oct. 1997
    Assuming that the string inspired, universal sum rules for soft

    supersymmetry-breaking terms, which have been recently found both in a wide

    class of four-dimensional superstrings and in supersymmertic gauge-Yukawa

    unified gauge models, are satisfied above and at the grand unification scale,

    we investigate theirlow energy consequences and derive sum rules in the

    superpartner spectrum of the minimal supersymmetric standard model., Technical report
  • Phenomenological implications of moduli-dominant SUSY breaking
    Yoshiharu Kawamura; Shaaban Khalil; Tatsuo Kobayashi, Nuclear Physics B, 502, 1-2, 37, 58, 29 Sep. 1997
    Elsevier, English, Technical report
  • Phenomenological implications of moduli-dominant SUSY breaking
    Y Kawamura; S Khalil; T Kobayashi, NUCLEAR PHYSICS B, 502, 1-2, 37, 58, Sep. 1997
    English
  • "Anomalous" U(1) symmetry in orbifold string models
    Tatsuo Kobayashi; Hiroaki Nakano, Nuclear Physics B, 496, 1-2, 103, 131, 07 Jul. 1997
    Elsevier, English, Technical report
  • Soft scalar-mass sum rule in gauge-Yukawa unified models and its superstring interpretation
    Y Kawamura; T Kobayashi; J Kubo, PHYSICS LETTERS B, 405, 1-2, 64, 70, Jul. 1997
    English
  • Notes on Curtright-Zachos Deformations of osp(1,2) and Super Virasoro Algebras
    Naruhiko Aizawa; Tatsuo Kobayashi; Haru-Tada Sato, Int.J.Mod.Phys. A12 (1997) 5867-5883, 25 Jun. 1997
    Based on the quantum superspace construction of $q$-deformed algebra, we

    discuss a supersymmetric extension of the deformed Virasoro algebra, which is a

    subset of the $q$-$W_{\infty}$ algebra recently appeared in the context of

    two-dimensional string theory. We analyze two types of deformed super-Virasoro

    algebra as well as their $osp(1,2)$ subalgebras. Applying our quantum

    superspace structure to conformal field theory, we find the same type of

    deformation of affine $sl(2)$ algebra., Technical report
  • Low-Energy Theory from Superstring Theory with Anomalous U(1) Symmetry.
    KAWAMURA YOSHIHARU; KOBAYASHI TATSUO, 素粒子論研究, 95, 1, A60-A61, A61, Apr. 1997
    Soryushiron Kenkyu, Japanese
  • Soft Scalar-Mass Sum Rule in Gauge-Yukawa Unified Models and Its Superstring Interpretation
    Yoshiharu Kawamura; Tatsuo Kobayashi; Jisuke Kubo, Phys.Lett. B405 (1997) 64-70, 14 Mar. 1997
    It is shown that a certain sum rule for soft supersymmetry-breaking scalar

    masses, which has been recently found in a certain class of superstring models,

    is universal for gauge-Yukawa unified models. To explain this coincidence, we

    argue that the low-energy remnant of the target-space duality invariance in the

    effective supergravity of compactified superstrings can be identified with the

    (broken) scale invariance in gauge-Yukawa unified models, and that gauge-Yukawa

    unification which is indispensable for the sum rule to be satisfied follows

    from the matching of anomalies., Technical report
  • A string-inspired ansatz for quark masses and mixing
    T Kobayashi; ZZ Xing, MODERN PHYSICS LETTERS A, 12, 8, 561, 571, Mar. 1997
    English
  • "Anomalous U(1) Symmetry in Orbifold String Models"(jointly worked)
    Nucl. Phys., B496, 103, 131, 1997
  • A String-inspired Ansatz for Quark Masses and Mixing
    Tatsuo Kobayashi; Zhi-zhong Xing, 26 Sep. 1996
    We propose a simple but realistic pattern of quark mass matrices at the
    string scale, which can be derived from orbifold models of superstring theory
    with no use of gauge symmetries. This pattern is left-right symmetric and
    preserves the structural parallelism between up and down quark sectors. Its
    phenomenological consequences on flavor mixing and $CP$ violation are
    confronted with current experiments at the weak scale by use of the
    renormalization-group equations in the framework of the minimal supersymmetric
    standard model. We find that good agreement is achievable without fine-tuning.
  • A String-inspired Ansatz for Quark Masses and Mixing
    Tatsuo Kobayashi; Zhi-zhong Xing, Mod.Phys.Lett. A12 (1997) 561-572, 26 Sep. 1996
    We propose a simple but realistic pattern of quark mass matrices at the

    string scale, which can be derived from orbifold models of superstring theory

    with no use of gauge symmetries. This pattern is left-right symmetric and

    preserves the structural parallelism between up and down quark sectors. Its

    phenomenological consequences on flavor mixing and $CP$ violation are

    confronted with current experiments at the weak scale by use of the

    renormalization-group equations in the framework of the minimal supersymmetric

    standard model. We find that good agreement is achievable without fine-tuning., Technical report
  • Specific Scalar Mass Relations in SU(3)*SU(2)*U(1) Orbifold Model
    Yoshiharu Kawamura; Tatsuo Kobayashi; Tohru Komatsu, 25 Sep. 1996
    We study flat directions and soft scalar masses using a $Z_3$ orbifold model
    with $SU(3) \times SU(2) \times U(1)$ gauge group and extra gauge symmetries
    including an anomalous $U(1)$ symmetry. Soft scalar masses contain $D$-term
    contributions and particle mixing effects after symmetry breaking and they are
    parametrized by a few number of parameters. Some specific relations among
    scalar masses are obtained.
  • Specific Scalar Mass Relations in SU(3)*SU(2)*U(1) Orbifold Model
    Yoshiharu Kawamura; Tatsuo Kobayashi; Tohru Komatsu, Phys.Lett. B400 (1997) 284-294, 400, 3/4, 284, 294, 25 Sep. 1996
    We study flat directions and soft scalar masses using a $Z_3$ orbifold model

    with $SU(3) \times SU(2) \times U(1)$ gauge group and extra gauge symmetries

    including an anomalous $U(1)$ symmetry. Soft scalar masses contain $D$-term

    contributions and particle mixing effects after symmetry breaking and they are

    parametrized by a few number of parameters. Some specific relations among

    scalar masses are obtained., Technical report
  • Generic Formula of Soft Scalar Masses in String Models
    Yoshiharu Kawamura; Tatsuo Kobayashi, 06 Aug. 1996
    We derive formula of soft supersymmetry breaking scalar masses from
    4-dimensional string models within a more generic framework. We consider
    effects of extra gauge symmetry breakings including an anomalous $U(1)$
    breaking through flat directions, that is, $D$-term and $F$-term contributions,
    particle mixing effects and heavy-light mass mixing effects. Some
    phenomenological implications are discussed based on our mass formula.
  • Generic Formula of Soft Scalar Masses in String Models
    Yoshiharu Kawamura; Tatsuo Kobayashi, Phys.Rev. D56 (1997) 3844-3859, 56, 7, 3844, 3859, 06 Aug. 1996
    We derive formula of soft supersymmetry breaking scalar masses from

    4-dimensional string models within a more generic framework. We consider

    effects of extra gauge symmetry breakings including an anomalous $U(1)$

    breaking through flat directions, that is, $D$-term and $F$-term contributions,

    particle mixing effects and heavy-light mass mixing effects. Some

    phenomenological implications are discussed based on our mass formula., Technical report
  • Quasi Yukawa fixed point due to decoupling of SUSY particles
    T Kobayashi; Y Yamagishi, PHYSICS LETTERS B, 381, 1-3, 169, 176, Jul. 1996
    English
  • Flat Directions in $Z_{2n}$ Orbifold Models
    Yoshiharu Kawamura; Tatsuo Kobayashi, Nucl.Phys. B481 (1996) 539-576, 01 Jul. 1996
    We study generic features related to matter contents and flat directions in

    $Z_{2n}$ orbifold models. It is shown that $Z_{2n}$ orbifold models have

    massless conjugate pairs, $R$ and $\overline R$, in certain twisted sectors as

    well as one of untwisted subsectors. Using these twisted sectors, $Z_{2n}$

    orbifold models are classified into two types. Conjugate pairs, $R$ and

    $\overline R$, lead to $D$-flatness as $\langle R \rangle = \langle \overline R

    \rangle \neq 0$. We investigate generic superpotentials derived from orbifold

    models so as to show that this direction is indeed a flat direction., Technical report
  • Soft scalar masses in string models with anomalous U(1) symmetry
    Y Kawamura; T Kobayashi, PHYSICS LETTERS B, 375, 1-4, 141, 148, May 1996
    English
  • Implications of nonuniversal soft masses for gauge coupling unification
    R Altendorfer; T Kobayashi, INTERNATIONAL JOURNAL OF MODERN PHYSICS A, 11, 5, 903, 920, Feb. 1996
    English
  • Quasi Yukawa Fixed Point due to Decoupling of SUSY Particles
    Tatsuo Kobayashi; Yoshio Yamagishi, Phys.Lett. B381 (1996) 169-176, 31 Jan. 1996
    We study effects of SUSY particle decouplings on a quasi fixed point (QFP) of

    Yukawa coupling. From renormalization group analysis it is shown that if the

    SUSY breaking scale $M_S$ is large ($\simg 1$TeV), effects of decoupling of

    Higgsinos and squarks raise the top Yukawa QFP. This tendency is enhanced in

    most cases of non-universal SUSY breaking. For the case of $M_S\siml 1$TeV, the

    decoupling of gluinos lowers $m_t^{\rm QFP}$. We checked some parameter

    dependencies for the top Yukawa QFP. The bottom-top Yukawa unified case is also

    studied. When top quark mass is measured more precisely, some patterns of soft

    mass spectra could be excluded if rather large initial top Yukawa coupling is

    realized by underlying theory., Technical report
  • Soft Scalar Masses in String Models with Anomalous $U(1)$ symmetry
    Yoshiharu Kawamura; Tatsuo Kobayashi, 30 Jan. 1996
    We obtain the low-energy effective theory from string models with anomalous
    $U(1)$ symmetry. The feature of soft supersymmetry breaking scalar masses and
    some phenomenological implications are discussed. We show that it is, in
    general, difficult to keep the degeneracy and the positivity of squared soft
    scalar masses at the Planck scale.
  • Soft Scalar Masses in String Models with Anomalous $U(1)$ symmetry
    Yoshiharu Kawamura; Tatsuo Kobayashi, Phys.Lett.B375:141-148,1996; ERRATUM-ibid.B388:867,1996, 30 Jan. 1996
    We obtain the low-energy effective theory from string models with anomalous

    $U(1)$ symmetry. The feature of soft supersymmetry breaking scalar masses and

    some phenomenological implications are discussed. We show that it is, in

    general, difficult to keep the degeneracy and the positivity of squared soft

    scalar masses at the Planck scale., Technical report
  • "Flat Directions in Z2n Orbifold Models", (jointly worked)
    Nucl. Phys., B481, 539, 576, 1996
  • Remarks on the Kielanowski parametrization of the Kobayashi-Maskawa matrix
    Tatsuo Kobayashi; Zhi-Zhong Xing, Modern Physics Letters A, 11, 31, 2531, 2537, 1996
    World Scientific Publishing Co. Pte Ltd, English
  • "Quantum Deformed igl(n) Algebra on Quantum Space", (jointly worked)
    Mod. Lett., 11, 7, 535, 543, 1996
  • Quasi Yukawa Fixed Point Under Non-universal soft SUSY Breaking.
    KOBAYASHI TATSUO; YAMAGISHI YOSHIO, 日本物理学会北陸支部・応用物理学会北陸・信越支部合同講演会講演予稿集, 1995, 18, Dec. 1995
    Japanese
  • Neutron Electric Dipole Moment under Non-Universal Soft SUSY Breaking Terms((3).Susy phenomenology, SUSY GUT and SUSY Breaking Mechanism,YITP workshop(Particle physics and its future perspective))
    Yamagishi Y, Soryushiron Kenkyu, 92, 1, A46, 20 Oct. 1995
    Soryushiron Kenkyu, Japanese
  • 29a-SG-7 Quasi Yukawa Fixed Point Under Non-universal soft SUSY Breaking
    Kobayashi Tatsuo; Yamagishi Yoshio, Abstracts of the meeting of the Physical Society of Japan. Sectional meeting, 1995, 1, 14, 14, 12 Sep. 1995
    The Physical Society of Japan (JPS), English
  • NEUTRON ELECTRIC-DIPOLE MOMENT UNDER NONUNIVERSAL SOFT SUSY BREAKING TERMS
    T KOBAYASHI; M KONMURA; D SUEMATSU; K YAMADA; Y YAMAGISHI, PROGRESS OF THEORETICAL PHYSICS, 94, 3, 417, 433, Sep. 1995
    English
  • Quasi Yukawa Fixed Point Under Non-universal soft SUSY Breaking.
    KOBAYASHI TATSUO; YAMAGISHI YOSHIO, 日本物理学会講演概要集(分科会), 1995, Autumn Pt 1, 14, 14, Sep. 1995
    The Physical Society of Japan (JPS), Japanese
  • NONUNIVERSAL SOFT SCALAR MASSES IN SUPERSTRING THEORIES
    T KOBAYASHI; D SUEMATSU; K YAMADA; Y YAMAGISHI, PHYSICS LETTERS B, 348, 3-4, 402, 410, Apr. 1995
    English
  • Non-universal SUSY breaking effects on Radiative SU(2)×U(1)breaking
    Kobayashi Tatsuo; Suematsu Daijiro; Yamada Kiyonori; Yamagishi Yoshio, Abstracts of the meeting of the Physical Society of Japan. Annual meeting, 50, 1, 17, 17, 16 Mar. 1995
    The Physical Society of Japan (JPS), Japanese
  • Non-universal SUSY breaking effects on Radiative SU(2)*U(1) breaking.
    KOBAYASHI TATSUO; SUEMATSU DAIJIRO; YAMADA KIYONORI; YAMAGISHI YOSHIO, 日本物理学会講演概要集(年会), 50th, 1, 17, Mar. 1995
    Japanese
  • "Quark Mass Matrices in Orbifold Models"
    Phys. Lett., 358, 3/4, 253, 258, 1995
  • "Selection Rules for Nonrenormalizable Couplings in Superstring Theories"
    Phys. Lett., 354, 3/4, 264, 270, 1995
  • "CP in Orbifold Models", (jointly worked)
    Phys. Lett., 343, 1/4, 122, 127, 1995
  • "Minimal String Unification and Yukawa Couplings in Orbifold Models"
    Int. J. Mod. Phys., 10, 10, 1393, 1411, 1995
  • MINIMAL STRING UNIFICATION AND CONSTRAINT ON HIDDEN SECTOR
    H KAWABE; T KOBAYASHI; N OHTSUBO, NUCLEAR PHYSICS B, 434, 1-2, 210, 230, Jan. 1995
    English
  • Supersting Unification and Soft SUSY Breaking Terms
    Kobayashi Tatsuo, Soryushiron Kenkyu, 90, 3, C81, C85, 20 Dec. 1994
    Soryushiron Kenkyu, English
  • 超弦理論から標準模型へ(第22回北陸合宿研究会の報告,地域スクール報告)
    小林 達夫, 素粒子論研究, 90, 2, B51, 20 Nov. 1994
    素粒子論グループ 素粒子研究編集部, Japanese
  • 超弦理論から標準模型へ
    小林達夫, 素粒子論研究, 90, 2, B51, Nov. 1994
    Japanese
  • Neutron Electric Dipole Moment under non-Universal Soft SUSY Breaking Terms.
    KOBAYASHI TATSUO; KONMURA MASAHIKO; SUEMATSU DAIJIRO; YAMADA KIYONORI; YAMAGISHI YOSHIO, 日本物理学会北陸支部・応用物理学会北陸・信越支部合同講演会講演予稿集, 1994, 11, Nov. 1994
    Japanese
  • Minimal String Unification in Orbifold Models(Superstring)
    Kobayashi Tatsuo, Soryushiron Kenkyu, 89, 4, D92, D94, 20 Jul. 1994
    Soryushiron Kenkyu, English
  • GAUGE COUPLING UNIFICATION DUE TO NONUNIVERSAL SOFT SUPERSYMMETRY BREAKING
    T KOBAYASHI; D SUEMATSU; Y YAMAGISHI, PHYSICS LETTERS B, 329, 1, 27, 32, Jun. 1994
    English
  • MINIMAL STRING UNIFICATION AND HIDDEN SECTOR IN Z(8) ORBIFOLD MODELS
    T KOBAYASHI, PHYSICS LETTERS B, 326, 3-4, 231, 237, May 1994
    English
  • LEVELS OF U(1)Y IN MINIMAL STRING MODEL ON Z(N)XZ(M) ORBIFOLDS
    H KAWABE; T KOBAYASHI; N OHTSUBO, PHYSICS LETTERS B, 325, 1-2, 77, 84, Apr. 1994
    English
  • "Study of Minimal String Unification in Z8 Orbifold Models", (jointly worked)
    Phys. Lett., 322, 4, 331, 339, 1994
  • GEOMETRICAL ASPECTS OF Z(N) ORBIFOLD PHENOMENOLOGY
    T KOBAYASHI; N OHTSUBO, INTERNATIONAL JOURNAL OF MODERN PHYSICS A, 9, 1, 87, 125, Jan. 1994
    English
  • Differential Calculi on h-deformed Bosonic and Fermionic Quantum Planes
    Tatsuo Kobayashi, Mod.Phys.Lett.A8:3741-3748,1993, 8, 39, 3741, 3748, 10 Aug. 1993
    We study differential calculus on h-deformed bosonic and fermionic quantum

    space. It is shown that the fermionic quantum space involves a parafermionic

    variable as well as a classical fermionic one. Further we construct the

    classical $su(2)$ algebra on the fermionic quantum space and discuss a mapping

    between the classical $su(2)$ and the h-deformed $su(2)$ algebras., Technical report
  • THE Z(4)XZ(4) ORBIFOLD MODEL AT AN ENHANCEMENT POINT AND THE 2(6) MODEL
    T KOBAYASHI; N OHTSUBO; K TANIOKA, INTERNATIONAL JOURNAL OF MODERN PHYSICS A, 8, 20, 3553, 3563, Aug. 1993
    English
  • Quantum deformed su(m/n) algebra and superconformal algebra on quantum superspace
    Tatsuo Kobayashi, Zeitschrift für Physik C Particles and Fields, 60, 1, 101, 109, Mar. 1993
    Springer-Verlag, English, Technical report
  • q-deformed superconformal algebra on quantum superspace
    Tatsuo Kobayashi; Tsuneo Uematsu, Phys.Lett. B306 (1993) 27-33, 15 Feb. 1993
    A quantum deformation of 4-dimensional superconformal algebra realized on

    quantum superspace is investigated. We study the differential calculus and the

    action of the quantum generators corresponding to $sl_q(1|4)$ which act on the

    quantum superspace. We derive deformed $su(1|2,2)$ algebras from the deformed

    $sl(1|4)$ algebra. Through a contraction procedure we obtain a deformed

    super-Poincar{\'e} algebra., Technical report
  • "q-Deformed Superconformal Algebra on Quantum Superspace", (jointly worked)
    Phys. Lett., 306, 1/2, 27, 33, 1993
  • "q-Deformed Conformal and Poincar(]E85EE[) Algebras on Quantum 4-Spinors", (jointly worked)
    Z. Phys., 58, 4, 559, 565, 1993
  • q-deformed conformal and Poincar{é} algebras on quantum 4-spinors
    Tatsuo Kobayashi; Tsuneo Uematsu, Z.Phys. C58 (1993) 559-566, 30 Oct. 1992
    We investigate quantum deformation of conformal algebras by constructing the

    quantum space for $sl_q(4,C)$. The differential calculus on the quantum space

    and the action of the quantum generators are studied. We derive deformed

    $su(4)$ and $su(2,2)$ algebras from the deformed $sl(4)$ algebra using the

    quantum 4-spinor and its conjugate spinor. The 6-vector in $so_q(4,2)$ is

    constructed as a tensor product of two sets of 4-spinors. The reality condition

    for the 6-vector and that for the generators are found. The q-deformed

    Poincar{\'e} algebra is extracted as a closed subalgebra., Technical report
  • 2p-H-2 Differential Calculus on Quantum Superspace and Deformation of Phase Space
    Kobayashi T, 秋の分科会講演予稿集, 1992, 1, 2, 2, 14 Sep. 1992
    The Physical Society of Japan (JPS), Japanese
  • Differential Calculus on Quantum Superspace and Deformation of Phase Space.
    小林達夫, 日本物理学会講演概要集(分科会), 1992, Autumn Pt 1, 2, Sep. 1992
    Japanese
  • Moduli Space of Orbifold and Phenomenological Aspects
    小林 達夫, Soryushiron Kenkyu, 85, 4, D3, D5, 20 Jul. 1992
    Soryushiron Kenkyu, Japanese
  • Moduli Space of Orbifold and Phenomenological Aspects.
    KOBAYASHI TATSUO, 素粒子論研究, 85, 4, D3-D5, Jul. 1992
    Japanese
  • Differential calculus on the quantum superspace and deformation of phase space
    Tatsuo Kobayashi; Tsuneo Uematsu, Zeitschrift für Physik C Particles and Fields, 56, 2, 193, 199, Jun. 1992
    Springer-Verlag, English, Technical report
  • "Shifted Z6 Orbifold Models and 1・4 Model", (jointly worked)
    Prog. Theor. Phys, 88, 2, 431, 442, 1992
  • "Correspondence of Z4×Z4 Orbifold Model and 26 Model"
    Suppl. Prog. Theor. Phys., 110, 277, 290, 1992
  • ALLOWED YUKAWA COUPLINGS OF ZNXZM ORBIFOLD MODELS
    T KOBAYASHI; N OHTSUBO, PHYSICS LETTERS B, 262, 4, 425, 431, Jun. 1991
    English
  • ANALYSES ON THE WILSON LINES OF ZN ORBIFOLD MODELS
    T KOBAYASHI; N OHTSUBO, PHYSICS LETTERS B, 257, 1-2, 56, 62, Mar. 1991
    English
  • ZN ORBIFOLD MODELS
    Y KATSUKI; Y KAWAMURA; T KOBAYASHI; N OHTSUBO; Y ONO; K TANIOKA, NUCLEAR PHYSICS B, 341, 3, 611, 640, Sep. 1990
    English
  • "Yukawa Coupling Condition of ZN Orbifold Models", (jointly worked)
    Phys. Lett., B245, 441, 446, 1990
  • Z8 AND Z12 ORBIFOLD MODELS
    Y KATSUKI; Y KAWAMURA; T KOBAYASHI; N OHTSUBO; Y ONO; K TANIOKA, PHYSICS LETTERS B, 227, 3-4, 381, 386, Aug. 1989
    English
  • GAUGE GROUPS OF ZN ORBIFOLD MODELS
    Y KATSUKI; Y KAWAMURA; T KOBAYASHI; N OHTSUBO; K TANIOKA, PROGRESS OF THEORETICAL PHYSICS, 82, 1, 171, 182, Jul. 1989
    English
  • Z4 AND Z6 ORBIFOLD MODELS
    Y KATSUKI; Y KAWAMURA; T KOBAYASHI; Y ONO; K TANIOKA; N OHTSUBO, PHYSICS LETTERS B, 218, 2, 169, 175, Feb. 1989
    English
  • Z7 ORBIFOLD MODELS
    Y KATSUKI; Y KAWAMURA; T KOBAYASHI; N OHTSUBO, PHYSICS LETTERS B, 212, 3, 339, 342, Sep. 1988
    English
  • Localication of Heterotic Anomalies on Various Hyper Surfaces of T^6/Z_4
    Phys. Rev., D
■ Books and other publications
■ Syllabus
  • 場の理論, 2024年, 学士課程, 理学部
  • 物理数学Ⅰ, 2024年, 学士課程, 理学部
  • 現代物理学, 2024年, 学士課程, 総合教育部
  • 相対論, 2024年, 学士課程, 理学部
  • 科学・技術の世界, 2024年, 学士課程, 全学教育
■ Affiliated academic society
  • 日本物理学会
■ Research Themes
  • Flavor structure and CP violation from string compactification
    Grants-in-Aid for Scientific Research
    01 Apr. 2023 - 31 Mar. 2028
    小林 達夫
    本研究の目的は、超弦理論のコンパクト空間の幾何学的性質に由来するクォーク・レプトンのフレーバー構造の解明である。ここ５年くらい２次元トーラスやオービフォルドなどのコンパクト空間の幾何学的対称性であるモジュラー対称性がクォーク・レプトンのフレーバー構造にどのように反映されるかというテーマに関し、系統的に研究を行ってきた。２０２３年度においては、その研究を２次元の直積でなない６次元トーラスやオービフォルドに拡張し、様々なフレーバー対称性が実現されることを示した。さらに、トーラスやオービフォルドなどの単純なコンパクト空間には限らず、カラビーヤウ多様体においても、そのモジュライ空間の特別な領域において、モジュラー対称性が現れ、湯川結合がモジュラー形式で与えられることを示した。
    さらにモジュラー形式は固定点近傍において、階層的な構造を示し、その振る舞いがクォーク・レプトンの質量と混合角の階層構造を導出するのに極めて重要であることを示し、様々な具体例を示した。このような質量と混合角の階層構造の再現には成功する一方で、モジュライが１つしかない場合においては、ＣＰ位相の再現が極めて困難であることを様々な具体例においては、直面した。その問題の根源を明らかにし、一般にモジュライが１つしかない場合においては、クォーク・レプトンの質量階層性の再現とＣＰ位相の再現が極めて困難であり、モジュライが複数必要で、１つのモジュライは質量と混合角の階層構造の再現を担い、別のモジュライはＣＰ位相の再現の役割をするという役割分担が有効であることを示した。
    上述のように位相も含めたモジュライの値が重要であるので、このモジュライの値をポテンシャル解析により、モジュライの値を決定も行った。
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 23K03375
  • 湯川結合とコンパクト空間
    科学研究費助成事業
    01 Apr. 2019 - 31 Mar. 2021
    小林 達夫
    本研究の目的は、超弦理論のコンパクト化の幾何学を起源として現れるクォーク・レプトンのフレーバー構造の探求である。特に、トーラスやオービフォルド空間がもつモジュラー対称性の解析を行い、背景磁場のあるもつコンパクト空間上のゼロモードの変換性を解析し、その対称性の有限部分群が、A4,S4やその拡張された群がフレーバー対称性となっていることを示した。特に、３世代模型を系統的に分類し、そのフレーバー対称性や湯川行列のパターン等の分類を行った。そして、具体的に、いくつかのコンパクト化の模型において、クォークの質量や混合角などの実験値の導出を可能性を調べた。また、このような実験値を再現するのに重要なパラメータがモジュライ場の真空期待値の値である。その値の決定は、長年、モジュライ固定の問題として認識されていた課題である。モジュライの真空期待値を決定を様々な3-formフラックスをもつコンパクト化において、系統的に行い、どのような値が実現可能か、そのときにCP対称性が自発的に破れる可能性はあるかなどを詳細に調べた。さらにカラビーヤウ多様体上のフレーバー構造やCP対称性の自発的破れなども研究を行った。
    そのようなトップダウン的なアプローチの一方で、ボトムアップアプローチとして、モジュラー対称性の有限部分群をフレーバー対称性としてもつ模型の構築や質量や混合角などの実験値の再現する模型を議論し、現在の実験での制限や将来実験への予言等について解析を行った。
    日本学術振興会, 新学術領域研究(研究領域提案型), 北海道大学, 19H04605
  • 超弦理論におけるモジュライの物理について
    科学研究費助成事業
    01 Apr. 2017 - 31 Mar. 2019
    小林 達夫
    本研究の目的は、コンパクト空間上の超弦理論の研究であり、その理論特有のモジュライの素粒子物理学的意味合いの研究である。コンパクト空間やモジュライが関わる物理現象を探求していくことは、コンパクト空間上の超弦理論の間接的な検証へつながる。
    本年度は、特にトーラスやオービフォルドがもつ幾何学的対称性に注目し、そのようなコンパクト空間上上のD-ブレーン模型のゼロモードが示す対称性を系統的に解析した。そのような対称性は世代間を変換させるような離散的なフレーバー対称性であることを示した。この対称性は、従来のフレーバー対称性と異なり、湯川結合なども変換するような大尉焼成である。さらに、モジュラー群の有限部分群の下で非自明に変換するモジュラー形式の多重項の新たな構成法を見出した。
    上述のような超弦理論における成果を踏まえて、場の理論のフレーバーに関する模型の構築も行った。従来、クォーク・レプトンの３世代にフレーバー対称性を課し、その対称性を新たに導入したスカラー場の真空期待値で破ることで、クォーク・レプトンの質量や混合角を導出することが、盛んになされてきた。新しい模型構築のアプローチとして、上述のモジュラー対称性の有限部分群を仮定し、３世代のクォーク・レプトンにその表現をアサインし、なおかつ、湯川結合や右巻きニュートリのマヨラナ質量もその有限部分群の非自明表現となるモジュラー形式であると仮定し、クォーク・レプトンのフレーバーの模型構築を行った。このアプローチは、新たに対称性を破るスカラー場の導入が必要なく、その点では、ミニマルなフレーバー模型となっている。また、コンパクト空間の幾何学的対称性とフレーバー対称性が関連付けられ、クォーク・レプトンの質量と混合角が導出されるので、非常に注文を集めている。
    日本学術振興会, 新学術領域研究(研究領域提案型), 北海道大学, 17H05395
  • Quest for the Ultimate Theory in terms of rich cosmophysical phenomena caused by fields and particles in the hidden sector
    Grants-in-Aid for Scientific Research
    27 Jun. 2014 - 31 Mar. 2018
    Kodama Hideo; KOBAYASHI Tatsuo; SODA Jiro; MIZOGUCHI Shun'ya; SUMITOMO Yoske; NOZAWA Masato
    We have systematically explored methods to probe whether the unified theory called string theory is the ultimate theory of Nature in terms of observations of phenomena caused by fields and particle in the hidden sector specific to superstring theory. As a result, we have proposed lots of new methods such as the observation of gravitational waves produced by the interaction between black holes and a scalar field called axion, observations of gamma rays from high-energy astrophysical objects and cosmic infrared background radiations, observations of electromagnetic and gravitational waves passing through axion dark matter, new particle searches by accelerator experiments, CMB observations of inflation in the early universe. Further, we have constructed some concrete examples of superstring compactifications that are consistent with both the standard model of elementary particles and cosmology.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), 26247042
  • Towards Unified Theories Beyond the Standard Model
    Grants-in-Aid for Scientific Research
    01 Apr. 2012 - 31 Mar. 2015
    KUGO Taichi; TANIMOTO Morimitsu; KUBO Jisuke; KOBAYASHI Tatsuo; MAEKAWA Nobuhiro
    This project aims to build Unified Theories of Elementary Particles which are expected to exist beyond the Standard Model, taking the sharp contrast of hierarchical generation mixing structures between quarks and leptons as a big clue.
    (1) The members of this project have individually produced their own good results; in particular, they elucidated that there must be some hidden discrete symmetries and E6 gauge symmetry behind those mixing structures as suggested by superstring theory.
    (2) They also organized Summer Institute every year and successfully promoted active young researchers in this field in Japan as well as in East Asia to make fruitful collaborations among them.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), 24340049
  • Low-energy effective field theory in realistic superstring thoery
    Grants-in-Aid for Scientific Research
    2013 - 2015
    Kobayashi Tatsuo
    Within type II and heterotic superstring theory, we have derived the gauge group of the standard model and its three chiral generations of quarks and letptons. We have also studied realization of experimental values of gauge couplings and quark/lepton masses and their mixing angles through perturbative calculations. Furthermore, we have studied concrtetely non-perturbative effects.
    We have also studied cosmological aspects such as inflation, dark matter, etc. We have proposed new types of inflation models and new scenarios of thermal history.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, Principal investigator, Competitive research funding, 25400252
  • The exploration of extradimensions in terms of a variety of cosmophysical phenomena caused by axionic moduli
    Grants-in-Aid for Scientific Research
    01 Apr. 2010 - 31 Mar. 2014
    KODAMA Hideo; OHTA Nobuyoshi; TAKAHASHI Fuminobu; NAKAYAMA Kazunori; OHTA Nobuyoshi; SHIBATA Masaru; MIZOGUCHI Shun'ya; KOBAYASHI Tatsuo; SODA Jiro; KOHRI Kazunori; ISHIBASHI Akihiro; IOKA Kuninito; TAKAHASHI Fuminobu; YOSHINO Hirotaka; NOZZWA Masato; NAGATA Ryo; KAWANAKA Norita; TOMIZAWA Shin'ya
    In order to open up a new observational/experimental window to the ultimate theory, we have studied axions from both the cosmophysics phenomenology aspect and the superstring/supergravity aspect and have published more than 200 papers. The main achievements are demonstarations of the axion bose nova phenemenon caused by a rotating black hole by numerical simulations and the discovery of its observability by gravitational wave experiments, derivation of a parameter range for axion to resolve the conflict between the high energy gamma-ray observations and the infrared background observation, evaluations of the influences of axions produced by the decay of heavy moduli on cosmic microwave background and derivation of constraints on the compactification of extra-dimensions on the basis of this estimation, derivation of constraints on elementary particle models from cosmological influences of axionic isocurvature perturbations and topological defects.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), High Energy Accelerator Research Organization, 22244030
  • Origin of Generations of Elementary Particles and Grand Unified Theories
    Grants-in-Aid for Scientific Research
    2008 - 2011
    KUGO Taichi; TANIMOTO Morimitsu; KUBO Jisuke; TERAO Haruhiko; KOBAYASHI Tatsuo; MAEKAWA Nobuhiro; BANDO Masako
    This project aims to build Unified Theories of Elementary Particles which are expected to exist beyond the Standard Model, taking the sharp contrast of hierarchical generation mixing structures between quarks and leptons as its important clue.(1) The members of this project have individually produced their own good results.(2) They also successfully organized Summer Institute once a year which provided the researchers in this area in Japan as well as in East Asia with chances to make fruitful collaborations.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Kyoto University, 20340053
  • Study on phenomenological aspects in superstring theory
    Grants-in-Aid for Scientific Research(基盤研究(C))
    2008 - 2011
    Tatsuo KOBAYASHI
    We have studied four-dimensional low-energy effective field theory, derived from superstring theory, in particular heterotic string theory on the orbifolds and magnetized/intersecting brane models. We have studied Abelian and non-Abelian discrete symmetries, which appear in these string models. Also we have studied their anomalies and found that the universal relations among certain anomalies. Furthermore, by explicit string computations we have shown stringy coupling selection rules, which seem to be difficult to understand from the symmetries of low-energy effective field theories.
    Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 京都大学, Principal investigator, Competitive research funding, 20540266
  • 弦理論のコンパクト化と現象論的性質についての研究
    科学研究費助成事業
    2008 - 2010
    小林 達夫; CHOI Kang-Sin
    超弦理論は、重力を含む統一理論の有力な候補である。超弦理論が本当に素粒子物理として、意味がある理論であるならば、低エネルギー有効理論として標準模型を再現するはずである。本研究の目的は、素粒子物理学の様々な現象論的性質が超弦理論の枠組みからどのようにして導出されるのかを研究することである。本年度我々は、まずF理論の現象論への応用について研究を行った。F理論は、IIB型超弦理論の強結合理論を記述すると思われているが、最近そのF理論の現象論への応用が盛んに研究されている。これまでのF理論の模型構築のシナリオはE8群から一度SU(5)群等の大統一理論を経て、標準模型を導出するようなアプローチであった。本年度我々は、SU(5)等の大統一理論を経るのではなく、直接標準模型を構築するような可能性を試み、かなり現実的なスペクトルを得ることに成功した。今後は、そのような研究を更に進めて、我々が構築した模型の質量行列や陽子崩壊、超対称性の破れなどの現象論的な性質の解析をする計画である。一方で我々は、背景磁場のあるブレーン模型の現象論的性質、特にフレーバー構造についての研究を行った。その結果によるとこのような模型では特定の非可換離散群がフレーバー対称性として現れることを示した。その起源は、コンパクト空間の幾何学的対称性ともともと大きなゲージ対称性が背景磁場のために破れる際に残った離散対称性の組み合わせであることを示した。今後はこの解析の結果を生かし、現実的なクォーク・レプトンの質量行列を導出する研究を行う予定である。
    日本学術振興会, 特別研究員奨励費, 京都大学, 08F08326
  • Impact of LHC on building physics beyond the standard model
    Grants-in-Aid for Scientific Research
    2004 - 2009
    MIHOKO Nojiri; KOBAYASHI Tatsuo; MAEKAWA Nobuhiro
    At LHC, non-standard model particles may be produced. Provided significant cross section and proper analysis, LHC experiment would be sensitive to them. Among the beyond the standard model, we focus on the models who have dark matter candidate, and study how to measure the mass and interaction from LHC data. We developed applications of MT2 distribution for mass determination, the determination of mass without relying on the end point of the distribution, and treatment of ISR in mass reconstructions.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research on Priority Areas, 16081207
  • String-derived flavor structures and their phenomenological aspects
    Grants-in-Aid for Scientific Research(基盤研究(C))
    2005 - 2007
    Tatsuo KOBAYASHI
    The purpose of this research is to clarify which flavor structures can be derived from superstring theory and to study their phenomenological implications.Recently, several discrete non-Abelian flavor symmetries were proposed to derive realistic mass matrices for quarks and leptons. However, their origins are not clear in 4D field theories. In 2006, we clarified that geometrical structure of compact space can provide their origins in superstring theories and typical flavor symmetries, which can appear from heterotic orbifold models, are D4 and Delta(54). In 2007, using these results, we studied which types of quark/lepton mass matrices can be realized from D4 flavor symmetries. Furthermore, when we consider supersymmetric theories, flavor symmetries constrain not only fermion mass matrices, but also mass matrices of their superpartners, i.e. supersymmetry breaking terms. We also studied specific patterns of supersymmetric breaking terms, which are predicted from the above D4 flavor symmetries.In addition, we computed higher order couplings, i.e. their moduli-dependence. We also studied moduli stabilization, and supersymmetry breaking and their phenomenological implications.
    Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 京都大学, Principal investigator, Competitive research funding, 17540251
  • World with Extra Dimensions and Unified Theory of Elementary Particles
    Grants-in-Aid for Scientific Research
    2004 - 2007
    KUGO Taichi; YANAGIDA Tsutomu; BANDO Masako; TANIMOTO Morimitsu; KOBAYASHI Tatsuo; MAEKAWA Nobuhiro
    T. Kugo, with M. Bando, considered new multi-quark bound states like penta-quarks using 5d supergravity and developed the computing method for masses of those states. He also calculated the electric and magnetic dipole moments of monopole and 'electron'.
    M. Bando, together with M. Tanimoto, also studied the possibility explaining neutrino mass matrix unifiedly with those of quarks and leptons in a category of models with a symetric matrix with zero elements.
    M Tanimoto considered models which possess various discrete flavor symmetries, and constructed several models which can actually explain mixings and mass matrices of quark and leptons.
    T. Yanagida proposed a theory of leptogenesis in which baryon number of our Universe is in fact generated through the decay of superheavy Majorana-type fermions. He also wrote a review paper on leptogenesis theory.
    T. Kobayashi started a systematic analysis of the flavor structures resulting from superstring theory. He stu died the mechanism for determining the moduli fields and spontaneous supersymmetry breaking.
    N. Maekawa found in a model with "E6 and horizontal symmetry" that a spontaneous breaking of CP symmetry resolves also the serious Supersymmetric CP problem explaining the Kobayashi-Maskawa phase properly. He also showed that his unified model with anomalous U(1) symmetry, if modified slightly, also gives a spontaneous supersymmetry breaking mechanism.
    S. Sugimoto, together with T. Sakai, constructed a novel holographic QCD model based on the superstring theory. They showed that the model can reproduce various properties of hadrons in our real world.
    We also achieved another big aim of this research project; namely we held the summer institute every year f or this four years as a core place where nation-wide cooperative researches in this field are organized and carried out. In fact, as shown by the fact that the Summer Institute in 2006 was held at Pohang in Korea, this Summer Institute is now becoming even a core of international collaborations in Asia.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Kyoto University, 16340071
  • 現実的湯川行列を導く機構とその超対称性の破れの項への影響
    科学研究費補助金(特定領域研究)
    2004 - 2005
    小林 達夫
    今年度は、超弦理論から導かれるフレーバー構造についての研究を行いました。超弦理論は、重力相互作用を含んだ統一理論の有力な候補です。そしてその弦理論は、我々の4次元時空以外に6次元コンパクト空間の存在を予言します。このコンパクト空間の幾何学的性質がフェルミオンのフレーバー構造を決定しています。しかし、これまではどのようなフレーバー構造が弦模型から導けるのか、どのようなパターンの湯川行列が導けるかといったことの系統的な解析はなされていませんでした。今年度は、heterotic Z6 orbifold models, intersecting D-brane modelsにおいて、そのような系統的な解析の第一歩を踏み出しました。前者についは現実的なquark/lepton質量行列が得られる可能性があるものの、後者の単純な模型では現実的な質量行列を導くことが難しいことが分かりました。さらに、上述のような弦模型の枠組みでは、湯川結合の強さ自体は、コンパクト空間の大きさや形を決めるようなモジュライ場の真空期待値の関数として与えられます。そしてその値が適当な値になったときに、現実的な質量行列が得られるわけです。したがって、モジュライの真空期待値の決定機構は、非常に重要です。このような目的で今年度はモジュライの真空期待値の様々な決定機構について研究しました。さらに、その際現れる超対称性の破れについても研究をしました。
    文部科学省, 特定領域研究, 京都大学, Principal investigator, Competitive research funding, 16028211
  • Flavor structure leading to hierarchical Yukawa couplings and Supersymmetry breaking
    Grants-in-Aid for Scientific Research(基盤研究(C))
    2002 - 2003
    Tatsuo KOBAYASHI
    Understanding the origin of fermion masses and mixing angles is one of important issues in particle physics. Within the framework of supersymmetric models, a mechanism to lead to realistic Yukawa matrices, in general, affects sfermion masses as well as the so-called A-terms. There are stringent experimental bounds on degeneracies of these SUSY breaking terms through FCNC processes. Taking into account these points, we have studied several types of flavor mechanisms.One type of flavor mechanisms which we have studied is supersymmetric standard models coupled with superconformal sectors, which have superconformal fixed points. In this type of models, superconformal dynamics generates large anomalous dimensions leading to hierarchically suppressed Yukawa couplings and at the same time controls sfermion masses so as to make them degenerate. Also we have studied flavor mechanism with 5D AdS background, which leads to the same result as the superconformal approach.We have also studied the model, which has S_3 symmetry as a flavor symmetry. Such symmetry has been studied in the literature, but it is broken at high energy. However, what is new in our model is that we extend the Higgs sector and impose the S_3 symmetry to the Higgs sector, too. The S_3 symmetry is broken around the electroweak scale. Such symmetry play a role in controlling SUSY breaking terms, so as to be consistent with experimental bounds on FCNC processes.Furthermore, we have also calculated Yukawa couplings in heterotic orbifold models including several moduli, e.g. continuous Wilson line moduli. One of our important results is that only the imaginary part of Kahler moduli contributes the physical CP phase in the Yukawa sector, while the other moduli, e.g. continuous and discrete Wilson lines do not contribute.
    Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 京都大学, Principal investigator, Competitive research funding, 14540256
  • ニュートリノ振動をめぐる理論的諸問題
    科学研究費助成事業
    2000 - 2003
    九後 太一; 前川 展祐; 小林 達夫; 川崎 雅裕; 波場 直之
    今年度の研究実績は次の通りである。
    九後は、二つの仮定1)クォーク・レプトンの質量行列が、異常U(1)電荷φ_iにより冪が与えられる因子化された形λ^{φ_i+φ_j}(Frogatt-Nielsen形)をとること、および2)このU(1)電荷φ_iがSU(5)GUTの構造を持つこと、を置くだけで、先ず、up型、down型クォークの質量データが必然的にレプトン側の牧-中川-坂田(MNS)混合行列U_{MNS}の大きな2-3混合を意味していることを示した。さらに太陽と大気ニュートリノの二乗質量差の比のデータをインプットすれば、1-2混合もまた必ず大きくなるということ、すなわちbi-large混合を導くことを示した。
    川崎は、宇宙背景放射の精密観測(WMAP)の結果から導かれた宇宙のバリオン密度と宇宙の軽元素合成理論から導かれるバリオン密度が有意にずれていることを説明できるシナリオをレプトン数の非対称や元素合成後のバリオン数の増大等を導入することによって作った。さらに、それを具体的に実現するものとして超対称性理論におけるQボール生成に基づくモデルを提案した。
    小林は、dilaton moduli場の素粒子の翼象論への重要な役割として、湯川結合の様々なmoduliへの依存性を計算した。そして4次元有効理論の結合の大きさを決める様々なdilaton moduli場の真空期待値の決定の機構を研究し、これらのmoduli場のインフレーション時での振舞いを調べた。
    前川は、異常U(1)を用いた大統一理論の研究を継続し、E_6におけるdoublet-triplet splittingを実現するよりシンプルなモデルを提唱しただけでな、doublet-triblet splittingを実現するため昔提唱されたsliding singlet機構を一般化した。また、E_6大統一理論においては、レプトンセクターの混合角が一般的にクォークセクターの混合角よりも大きくなることを指摘し、その同じ構造がホリゾンタル対称性導入によるFCNCのsuppressionを自然に実現することを指摘した。また、ホリゾンタル対称性を持つE_6のヒッグズセクターを構築した。
    日本学術振興会, 特定領域研究, 京都大学, 12047214
  • 超対称性の破れと超弦理論の現象論的性質
    Competitive research funding
  • Supersymmetry Breaking and Superstring Phenomenology
    Competitive research funding