Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

We study thermal effects on a decay process of a false vacuum in type IIA string theory. At finite temperature, the potential of the theory is corrected and also thermally excited modes enhance the decay rate. The false vacuum can accommodate a string-like object. This cosmic string makes the bubble creation rate much larger and causes an inhomogeneous vacuum decay. We investigate thermal corrections to the DBI action for the bubble/string bound state and discuss a thermally assisted tunneling process. We show that thermally excited states enhance the tunneling rate of the decay process, which makes the life-time of the false vacuum much shorter.

DOI： 10.1016/j.physletb.2016.09.050

Language：English   Publishing type：Research paper (scientific journal)  

Abstract: We consider a decay of a false vacuum in flux compactifications of type IIB string theory and study a catalytic effect for a phase transition induced by a new type of impurities. We concentrate on the large N dual of a D5-brane/anti-D5-brane system which has a rich vacuum structure. We show that D3-branes wrapping the 3-cycles can form a baryon bound state with a monopole. We find that these baryon-like objects can make the lifetime of the metastable vacuum shorter.

DOI： 10.1007/JHEP06(2016)029

Language：English   Publishing type：Research paper (scientific journal)  

Abstract: We study dynamics of a cosmic string in a metastable brane configuration in Type IIA string theory. We first discuss a decay process of the cosmic string via a fuzzy brane (equivalently bubble/string bound state) by neglecting gravitational corrections in ten-dimension. We find that depending on the strength of the magnetic field induced on the bubble, the decay rate can be either larger or smaller than that of O(4) symmetric bubble. Then, we investigate gravitational corrections to the fuzzy brane by using the extremal black N S-five brane solution, which makes the lifetime of the metastable state longer.

DOI： 10.1007/JHEP06(2015)098

Language：English   Publishing type：Research paper (scientific journal)  

We investigate dielectric branes in false vacua in type IIB string theory. The dielectric branes are supported against collapsing by lower energy vacua inside spherical or tubelike branes. We claim that such branes can be seeds for semiclassical (or quantum mechanical) decay of the false vacua, which makes the lifetime of the false vacua shorter. Also, we discuss a topology change of a bubble corresponding to the fuzzy monopole triggered by dissolving fundamental strings.

DOI： 10.1103/PhysRevD.91.126002

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

KIKAN education KADAI-KYOGAKU (interdisciplinary collaborative learning of social issues)

DOI： 10.15017/1495422

Language：English   Publishing type：Research paper (scientific journal)  

Abstract: We study radiation of supersymmetric particles from an Aharonov-Bohm string associated with a discrete R-symmetry. Radiation of the lightest supersymmetric particle, when combined with the observed dark matter density, imposes constraints on the string tension or the freeze-out temperature of the particle. We also calculate the amplitude for Aharonov-Bohm radiation of massive spin 3/2 particles.

DOI： 10.1007/JHEP02(2015)164

Language：English   Publishing type：Research paper (scientific journal)  

We investigate cosmological constraints on phenomenological models with discrete gauge symmetries by discussing the radiation of standard model particles from Aharonov-Bohm strings. Using intersecting D-brane models in Type IIA string theory, we demonstrate that Aharonov-Bohm radiation, when combined with cosmological observations, imposes constraints on the compactification scales.

DOI： 10.1007/JHEP01(2014)049

Language：English   Publishing type：Research paper (scientific journal)  

We study the spontaneous R-symmetry breaking model and investigate the cosmological constraints on this model due to the pseudo Nambu-Goldstone boson, R-axion. We consider the R-axion which has relatively heavy mass in order to complement our previous work. In this regime, model parameters, R-axions mass and R-symmetry breaking scale, are constrained by Big Bang Nucleosynthesis and overproduction of the gravitino produced from R-axion decay and thermal plasma. We find that the allowed parameter space is very small for high reheating temperature. For low reheating temperature, the U(1)R breaking scale fa is constrained as fa < 10^12-14 GeV regardless of the value of R-axion mass.

DOI： 10.1088/1475-7516/2014/01/024

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： 10.1007/JHEP01(2014)165

Language：English   Publishing type：Research paper (scientific journal)  

We study stabilization of an unstable cosmic string associated with spontaneously broken U(1) _R symmetry, which otherwise causes a dangerous roll-over process. We demonstrate that in a gauge mediation model, messengers can receive enough corrections from the thermal plasma of the supersymmetric standard model particles to stabilize the unstable modes of the string.

DOI： 10.1007/JHEP05(2013)091

Language：English   Publishing type：Research paper (scientific journal)  

We show that a cosmic string associated with spontaneous U(1) _R symmetry breaking gives a constraint for supersymmetric model building. In some models, the string can be viewed as a tube-like domain wall with a winding number interpolating a false vacuum and a true vacuum. Such string causes inhomogeneous decay of the false vacuum to the true vacuum via rapid expansion of the radius of the tube and hence its formation would be inconsistent with the present Universe. However, we demonstrate that there exist metastable solutions which do not expand rapidly. Furthermore, when the true vacua are degenerate, the structure inside the tube becomes involved. As an example, we show a "bamboo"-like solution, which suggests a possibility observing an information of true vacua from outside of the tube through the shape and the tension of the tube.

DOI： 10.1007/JHEP03(2013)159

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： 10.1088/1475-7516/2013/04/043

Language：English   Publishing type：Research paper (scientific journal)  

In the standard model, the electroweak Z string can end on a Nambu monopole, whose mass is calculated to be 689 GeV from the current precise experimental data assuming the new particle with mass 125 GeV to be the Higgs boson. We study an extension of the standard model with additional singlet and triplet Higgs fields in the framework of N=1 supersymmetric field theory by using a D-brane configuration in type IIA string theory. We construct a D-brane configuration describing the electroweak symmetry breaking, and find a single D2-brane configuration describing a Z string and a Nambu monopole attached by a Z string in the standard model without an adjoint Higgs field. We further find a single D2-brane configuration describing a composite of a 't Hooft-Polyakov monopole and a Nambu monopole attached by a Z string in an extended standard model with an adjoint Higgs field. We compute the binding energy of the 't Hooft-Polyakov and Nambu monopoles by solving a minimal surface area of a D2-brane.

DOI： 10.1103/PhysRevD.87.045006

Language：English   Publishing type：Research paper (international conference proceedings)  

It has been known that in a wide class of direct gauge mediation models, the gaugino masses vanish at leading order in SUSY breaking. Recently, this phenomenon is understood in connection with the global structure of vacua in O'Raifeartaigh-type models. We review recent developments on this topic.

DOI： 10.1142/S0217751X11054565

Language：English   Publishing type：Research paper (scientific journal)  

We discuss constraints from cosmology on the models with direct gauge mediation based on the ISS supersymmetry breaking models. It is a generic feature that the ISS models possess a U(1) symmetry which is eventually spontaneously broken, when the models are based on the gauge symmetries with complex representations. We show that the resultant pseudo Nambu-Goldstone boson causes problems in cosmology, which leads to severe constraints on the models. We also show that most parameter space of the models can be probed by observing gravitational waves emitted from the cosmic string network when the U(1) symmetry is a gauge symmetry.

DOI： 10.1007/JHEP08(2011)044

Language：English   Publishing type：Research paper (scientific journal)  

In a wide class of direct and semidirect gauge mediation models, it has been observed that the gaugino masses vanish at leading order. It implies that there is a hierarchy between the gaugino and sfermion masses, invoking a fine-tuning problem in the Higgs sector via radiative corrections. In this paper, we explore the possibility of solving this anomalously light gaugino problem exploiting strong conformal dynamics in the hidden sector. With a mild assumption on the anomalous dimensions of the hidden sector operators, we show that the next-to-leading order contributions to the gaugino masses can naturally be in the same order as the sfermion masses. The μ/B_μ problem is also discussed.

DOI： 10.1103/PhysRevD.83.125010

Language：English   Publishing type：Research paper (scientific journal)  

In direct gauge mediation, gaugino masses often vanish at the leading order of supersymmetry breaking. Recently, this phenomenon is understood in connection with the global structure of vacua in O'Raifeartaigh-type models. In this note, we further explore a connection between gaugino masses and the landscape of vacua in more general situations, focusing on a few examples which demonstrate our idea. In particular, we present a calculable model with non-vanishing leading order gaugino masses on the lowest energy vacuum.

DOI： 10.1007/JHEP01(2011)093

Language：English   Publishing type：Research paper (scientific journal)  

We review recent works on supersymmetry breaking and gauge mediation. We survey our current understanding of dynamical supersymmetry-breaking mechanisms and describe new model-building tools that use duality, metastability, and stringy construction. We discuss phenomenological constraints and their solutions, paying particular attention to gaugino masses and electroweak symmetry breaking.

DOI： 10.1146/annurev.nucl.012809.104540

Language：English   Publishing type：Research paper (scientific journal)  

The smallest integer t for which the Wilson loop W ^t fails to exhibit area law is known as the confinement index of a given field theory. The confinement index provides us with subtle information on the vacuum properties of the system. We study the behavior of the Wilson and 't Hooft loops and compute the confinement index in a wide class of N=1 supersymmetric gauge theories. All possible electric and magnetic screenings are taken into account. The results found are consistent with the θ periodicity, and whenever such a check is available, with the factorization property of Seiberg-Witten curves.

DOI： 10.1016/j.nuclphysb.2009.10.018

Language：English   Publishing type：Research paper (scientific journal)  

We present a general scheme for finding or creating a metastable vacuum in supersymmetric theories. By using the formalism, we show that there is a parameter region where a metastable vacuum exists in the Wess-Zumino model coupled to messenger fields. This model serves as a perturbative renormalizable model of direct gauge mediation.

DOI： 10.1016/j.physletb.2009.03.057

Language：English   Publishing type：Research paper (scientific journal)  

In the gauge mediation mechanism, the effects of the hidden sector are characterized by a set of correlation functions of the global symmetry current of the hidden sector. We present methods to compute these correlators in cases with strongly coupled hidden sectors. Several examples are presented to demonstrate the technique explicitly.

DOI： 10.1016/j.nuclphysb.2008.09.017

Language：English   Publishing type：Research paper (scientific journal)  

We show that the perturbation of an N = 2 supersymmetric gauge theory by a superpotential linear in the Kähler normal coordinates of the Coulomb branch, discussed in [H. Ooguri, Y. Ookouchi, C.S. Park, Metastable vacua in perturbed Seiberg-Witten theories, arXiv: 0704.3613 [hep-th]], is equivalent to the perturbation by Fayet-Iliopoulos terms. It follows that the would-be meta-stable vacuum at the origin of the normal coordinates in fact preserves N = 1 supersymmetry unless the superpotential is truncated to a finite-degree polynomial of the adjoint scalar fields. We examine the criteria for supersymmetry breaking under a perturbation by Fayet-Iliopoulos terms and present a general classification of non-supersymmetric critical points. In some explicit examples, we are also able to study local stability of these points and demonstrate that, if the perturbation is chosen appropriately, they indeed correspond to supersymmetry-breaking vacua. Relations of these constructions to flux compactifications and geometric meta-stability are also discussed.

DOI： 10.1016/j.nuclphysb.2008.01.014

Language：English   Publishing type：Research paper (scientific journal)  

We show that, for a generic choice of a point on the Coulomb branch of any N = 2 supersymmetric gauge theory, it is possible to find a superpotential perturbation which generates a metastable vacuum at the point. For theories with SU(N) gauge group, such a superpotential can be expressed as a sum of single-trace terms for N = 2 and 3. If the metastable point is chosen at the origin of the moduli space, we can show that the superpotential can be a single-trace operator for any N. In both cases, the superpotential is a polynomial of degree 3N of the vector multiplet scalar field.

Language：English   Publishing type：Research paper (scientific journal)  

We show that a large class of phenomenologically viable models for gauge mediation of supersymmetry breaking based on meta-stable vacua can be realized in local Calabi-Yau compactifications of string theory.

DOI： 10.1016/j.physletb.2007.06.056

Language：English   Publishing type：Research paper (scientific journal)  

The supersymmetric SU(NC) Yang-Mills theory coupled to NF matter fields in the fundamental representation has metastable vacua with broken supersymmetry when NC<NF<32NC. By gauging the flavor symmetry, this model can be coupled directly to the standard model. We show that it is possible to make a slight deformation to the model so that gaugino masses are generated and the Landau pole problem can be avoided. The deformed model has simple realizations on intersecting branes in string theory, where various features of the metastable vacua are encoded geometrically as brane configurations.

DOI： 10.1103/PhysRevD.75.045022

Language：English   Publishing type：Research paper (scientific journal)  

We study vacuum structure of N = 1 supersymmetric quiver gauge theories which can be realized geometrically by D-brane probes wrapping cycles of local Calabi-Yau three-folds. In particular, we show that the A₂ quiver theory with gauge group U (N₁) × U (N₂) with frac(1, 2) N₁ < N₂ < frac(2, 3) N₁ has a regime with an infrared free description that is partially magnetic and partially electric. Using this dual description, we show that the model has a landscape of inequivalent meta-stable vacua where supersymmetry is dynamically broken and all the moduli are stabilized. Each vacuum has distinct unbroken gauge symmetry. The gaugino masses are generated by radiative corrections, and we are left with the bosonic pure Yang-Mills theory in the infrared. We also identify the supersymmetric vacua in this model using their infrared free descriptions and show that the decay rates of the supersymmetry breaking vacua can be made parametrically small.

DOI： 10.1016/j.nuclphysb.2006.08.009

Language：English   Publishing type：Research paper (scientific journal)  

We identify configurations of intersecting branes that correspond to the meta-stable supersymmetry breaking vacua in the four-dimensional N = 1 supersymmetric Yang-Mills theory coupled to massive flavors. We show how their energies, the stability properties, and the decay processes are described geometrically in terms of the brane configurations.

DOI： 10.1016/j.physletb.2006.08.035

Language：English   Publishing type：Research paper (scientific journal)  

We study four-dimensional N = 1 Spin (10) gauge theory with a single spinor and N_Q vectors at the superconformal fixed point via the electric-magnetic duality and a-maximization. When gauge invariant chiral primary operators hit the unitarity bounds, we find that the theory with no superpotential is identical to the one with some superpotential at the infrared fixed point. The auxiliary field method in the electric theory offers a satisfying description of the infrared fixed point, which is consistent with the better picture in the magnetic theory. In particular, it gives a clear description of the emergence of new massless degrees of freedom in the electric theory.

DOI： 10.1016/j.nuclphysb.2005.11.024

Language：English   Publishing type：Research paper (scientific journal)  

We study large classes of renormalization group flows, driven by scalar expectation values or mesonic superpotential terms, away from the conformal fixed points of the 4d supersymmetric gauge theories with A D E-type superpotentials. The a-maximization procedure allows us to compute the R charges and to check the a-theorem conjecture. For a theory obtained by Higgsing the D_k+2 theory, we use the magnetic dual description proposed by Brodie to determine the parameter region where the resulting theory is at a non-trivial conformal fixed point.

DOI： 10.1016/j.nuclphysb.2005.10.038

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

We present two results concerning the relation between poles and cuts by using the example of N=1 U(N_c) gauge theories with matter fields in the adjoint, fundamental and anti-fundamental representations. The first result is the on-shell possibility of poles, which are associated with flavors and on the second sheet of the Riemann surface, passing through the branch cut and getting to the first sheet. The second result is the generalization of hep-th/0311181 (Intriligator, Kraus, Ryzhov, Shigemori, and Vafa) to include flavors. We clarify when there are closed cuts and how to reproduce the results of the strong coupling analysis by matrix model, by setting the glueball field to zero from the beginning. We also make remarks on the possible stringy explanations of the results and on generalization to SO(N_c) and USp(2N_c) gauge groups.

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

We studied the phase structures of
supersymmetric SO(Nc) gauge theory with Nf flavors in the vector representation as we deformed the
supersymmetric QCD by adding the superpotential of arbitrary polynomial for the adjoint chiral scalar field. Using weak and strong coupling analyses, we determined the most general factorization forms for various breaking patterns. We observed all kinds of smooth transitions for quartic superpotential.

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Event date： 2015.12

Language：English   Presentation type：Oral presentation (general)  

Venue：高エネルギー加速器研究機構   Country：Japan  

Event date： 2015.12

Language：English  

Venue：京都大学　基礎物理学研究所   Country：Japan  

Event date： 2015.9

Language：Japanese  

Venue：京都大学　基礎物理学研究所   Country：Japan  

Event date： 2015.8

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛知県蒲郡市西浦町　ホテルたつき   Country：Japan  

Event date： 2015.6 - 2015.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：International Center for Theoretical Physics, Trieste,   Country：Italy  

Event date： 2015.2

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：理化学研究所   Country：Japan  

Event date： 2015.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学理学部　素粒子論研究室   Country：Japan  

Event date： 2014.7

Language：English   Presentation type：Oral presentation (general)  

Venue：京都大学　基礎物理学研究所   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都大学　理学部   Country：Japan  

ディスクリート対称性は弦理論を用いたモデルビルディングにしばしば登場する。バンクス－サイバーグの最近の議論に基づくと、そうしたディスクリート対称性はゲージ化されている必要がある。この場合、Aharonov-Bohm string/ particleが理論に存在する。Intersecting Brane modelを具体的に用いることで、Aharonov-Bohm stringからスタンダードモデルの粒子が放出されることを示し、それらが宇宙論的に与える影響を議論する。

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪市立大学　理学部   Country：Japan  

ディスクリート対称性は弦理論を用いたモデルビルディングにしばしば登場する。バンクス－サイバーグの最近の議論に基づくと、そうしたディスクリート対称性はゲージ化されている必要がある。この場合、Aharonov-Bohm string/ particleが理論に存在する。Intersecting Brane modelを具体的に用いることで、Aharonov-Bohm stringからスタンダードモデルの粒子が放出されることを示し、それらが宇宙論的に与える影響を議論する。

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都大学　理学部   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：茨城大学　理学部   Country：Japan  

Language：English   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：大阪大学　理学部   Country：Japan  

Event date： 2019.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：信州大学   Country：Japan  

Event date： 2016.1

Language：English  

Venue：沖縄科学技術大学院大学 OIST   Country：Japan  

Event date： 2015.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：高エネルギー加速器研究機構   Country：Japan  

Event date： 2014.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：佐賀大学   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Language：Japanese   Publishing type：Internal/External technical report, pre-print, etc.  

Language：Japanese   Publishing type：Internal/External technical report, pre-print, etc.  

Language：Japanese   Publishing type：Internal/External technical report, pre-print, etc.  

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc.