2012年度のセミナー

Date/Place 11 Mar. (Mon.) 15:30～ / H711
Name Masaki Murata (Institute of Physics ASCR, Czech)
Title Relationship between Marginal Deformation Parameters in Boundary CFT and Cubic SFT (slides)
Abstract Witten's cubic string field theory (Cubic SFT) has a class of solutions called "marginal deformation solutions". They are expected to be related to the marginal deformations of the conformal field theory (CFT) with corresponding boundary operators. In this talk I will show this relationship quantitatively.

　

Date/Place 19 Feb. (Tue.) 14:00～ / H711
Name Tatsu Takeuchi (Virginia Tech.)
Title Some Mutant Forms of Quantum Mechanics (slides)
Abstract In order to progress our understanding of Quantum Mechanics, we advocate what we call the "geneticist's approach" in which we introduce mutations to the mathematical genotypes of Quantum Mechanics and study how it affects the physical phenotypes of the theory. We show a few examples of such "mutations" and how the predictions of Quantum Mechanics are affected. We argue that in the process, the physical meanings of various mathematical aspects of Quantum Mechanics will be clarified, and further possible directions of evolution will be evinced.

　

Date/Place 29 Jan. (Tue.) 15:30～ / H711
Name Tetsutaro Higaki (RIKEN)
Title Cosmology in LARGE volume string models (slides)
Abstract In this seminar, we will discuss cosmology in supergravities which can be derived from LARGE volume string compactifications, while focusing on dark radiation. For a natural realization of LARGE extra dimension, swiss-cheese Calabi-Yau spaces will be considered in type IIB orientifolds in flux vacua. On such a compactification, ultralight string-theoretic axion(s) can always appear at low energies, and it plays a role in dark radiation suggested by observations of He-4 and CMB etc. If we have time, I would like to show that such LARGE volume scenario can be a natural and promising candidate also for explaining baryogenesis and inflation in string theory.

　

Date/Place 22 Jan. (Tue.) 15:30～ / H711
Name Johannes Schmude (RIKEN)
Title SCFTs from gravity's point of view
Abstract Gauge/string duality relates superconformal field theories (SCFTs) to string- and supergravity theories on the product of anti-de Sitter space and a suitable compact, internal manifold. The physical properties of the dual gauge theory are directly related to the geometry of the internal manifold, with a large class of theories given by Sasaki-Einstein manifolds. In this talk, I will discuss ongoing work relating the spectrum and multiplet structure of representations of the SCFTs to geometric properties of such spaces. One result is the calculation of the so-called superconformal index from supergravity. The talk will begin with an introduction to the essential aspects of gauge/string duality.

　

Date/Place 15 Jan. (Tue.) 15:30～ / H711
Name Yuta Hamada (Kyoto Univ.)
Title Bare Higgs mass at Planck scale (slides)
Abstract We compute one and two loop quadratic divergent contributions to the bare Higgs mass in terms of the bare couplings in the Standard Model (SM). We approximate the bare couplings, defined at the ultraviolet cutoff scale, by the MSbar ones at the same scale, which are evaluated by the two loop renormalization group equations for the Higgs mass around 126GeV in the SM. We obtain the cutoff scale dependence of the bare Higgs mass, and examine where it becomes zero. We find that when we take the current central value for the top quark pole mass, 173GeV, the bare Higgs mass vanishes if the cutoff is about 10^{23}GeV. With a 1.3 sigma smaller mass, 170GeV, the scale can be of the order of the Planck scale.

　

Date/Place 8 Jan. (Tue.) 15:30～ / H711
Name Andrey Tayduganov (Osaka Univ.)
Title New Physics search in B-> D l nu and B-> D^* l nu
Abstract Recent experimental results for the ratio of the branching fractions of decays B-> D^{(*)} tau nu and B-> D^{(*)} mu nu came as a surprise and lead to a discussion of possibility to constraining New Physics through these modes. We show that these decay channels can provide us with quite good constraints of the New Physics couplings. Studying various angular distributions, we demonstrate that some of the angular coefficients and asymmetries, which can be determined experimentally, turn out to be sensitive to New Physics and therefore can provide a good test of the presence of the new type operators.

　

Date/Place 18 Dec. (Tue.) 15:30～ / H711
Name Ken-Ichi Aoki (Kanazawa Univ.)
Title Global minimization of the effective potential by solving weak non-perturbative renormalization group equation.
Abstract The dynamical chiral symmetry breaking is analyzed in the framework of the non-perturbative renormalization group, where the scale dependent Wilsonian effective action of fermions is obtained by solving the differential equation. In case that the dynamical symmetry breaking occurs, the effective action starts to show some singularities at a finite scale while it is a smooth regular function at the initial scale. Taking the Nambu-Jona-Lassinio model with large N limit, we define the weak renormalization group equation to descrive such spontaneous emergence of singuralities. Then the weak solution gives us a convexized effective potential and automatic global minimization of the free energy even in case of the first order phase transtion caused by the finite density. The similar method is also applied to thermal and dense QCD.

　

Date/Place 11 Dec. (Tue.) 15:30～ / H711
Name Koji Hashimoto (Osaka U.)
Title Landscape in Boundary String Field Theory (slides)
Abstract String field theory is a non-perturbative formulation of string theory allowing one to explore string theory vacua and off-shell structure. We solve the equation of motion of boundary string field theory with stringy massive states, and find a large number of new non-perturbative vacua. Possible cosmological applications and generalization of Sen's conjecture on D-brane annihilation are discussed.
Refs Based on a work with M.Murata (at Czech), arXiv:1211.5949

　

Date/Place 4 Dec. (Tue.) 15:00~ / H711
Name Hikaru Kawai (Kyoto U.)
Title Multiverse and the Naturalness Problem (slides)
Abstract TBA

　

Date/Place 27 Nov. (Tue.) 15:30～ / H711
Name Johny Robert Johansson (RIKEN)
Title Dynamical Casimir effect in superconducting microwave circuits (slides)
Abstract An intriguing consequence of quantum mechanics is that the vacuum is not empty. In fact, quantum theory predicts that it teems with virtual particles fleeting in and out of existence. These vacuum fluctuations are responsible for several measurable effects, producing for example the Lamb shift and Casimir forces. The dynamical Casimir effect (DCE) is an example of a dynamical quantum vacuum phenomena, where a nonadiabatic time-dependent boundary condition - for example a relativistic accelerating mirror - can amplify vacuum fluctuations and produce real observable photons. Here I will present a theoretical proposal for observing the DCE in a quantum mechanical superconducting waveguide, with emphasis on photon statistics and correlations that can be used as signatures in experimental measurements of the effect. I will also briefly present and discuss experimental data from measurements of the dynamical Casimir radiation in a superconducting microwave circuit.

　

Date/Place 20 Nov. (Tue.) 15:30～ / H711
Name Koichi Yamawaki (KMI)
Title Discovering Walking Technicolor at LHC
Abstract Origin of Mass is the most urgent issue of the modern particle physics. We are now at exciting time to settle this issue by the LHC experiments. Recently a boson around 125 GeV was discovered at LHC, with its current data roughly consistent with the Higgs boson responsible for the Origin of Mass in the standard model. However, there are many unsolved problems in the standard model, one of which would be the mystery of the very nature of the Higgs boson at such a mass range, often called ``naturalness problem'' or ``hierarchy problem''. Technicolor is the one of the new physics to solve this problem, based on the analogy of QCD where mass of the particles (typically the nucleon and the rho meson, etc.) is generated dynamically from ``nothing'', i.e., even from the massless quarks and gluons in the ideal limit. However, the original version of the Technicolor was dead long time ago for serious contradiction with the experiments. It is the Walking Technicolor (WTC) proposed by us back in 1986 that solves this difficulty by a (almost) scale-invariant gauge dynamics. In contrast to QCD whose gauge coupling is ``running'' (changing value depending upon the energy scale) and hence violates the scale symmetry, the gauge coupling of WTC is almost non-running (``walking''). When we proposed WTC, we actually predicted ``techni-dilaton'' as a Nambu-Goldstone boson of the scale symmetry, which is a composite scalar boson made of a pair of the techni-fermion and anti-technifermion and is expected to become massless in the ideal limit of the exact scale symmetry. Hence a discovery of such a composite scalar particles much lighter than the typical WTC scale on TeV should be a smoking gun of the WTC. I will show that the current LHC data on the 125 GeV boson can be identified with the techni-dilaton even better than the standard model Higgs boson. The KMI lattice group is studying such a scale-invarinat dynamics of WTC from the first principle through computer simulations by the KMI computer ``phi''φ.

　

Date/Place 13 Nov. (Tue.) 15:30～ / H711
Name Piljin Yi (KIAS)
Title Wall-Crossing and Quiver Invariants (slides)
Abstract In string theory, geometry and quantum states are tightly connected. In particular, this leads to the wall-crossing problem where (non-)existence of so-called calibrated cycles can be figured out by solving relatively simple class of Schroedinger problems, or vice versa. We start with a one-slide review of the Kontsevich-Soibelman (KS) solution to the wall-crossing problem and then proceed to direct and comprehensive physics counting of BPS states that eventually connects to KS. We also asks what input data is needed for either approaches to produce complete BPS spectra, and this naturally leads to the BPS quiver representation of BPS states and the new notion of quiver invariants. We propose a simple geometrical conjectures that can segregate BPS states in Higgs phases of the BPS quiver dynamics to those that experience wall-crossing and those that do not, and give proofs for all cyclice Abelian quivers. We close with explanation of how physics distinguishes two such classes of BPS states.

　

Date/Place 7 Nov. (Tue.) 11:00～ / H711 (informal)
Name Taro Kimura (RIKEN)
Title Recent topics on lattice fermions (slides)
Abstract We would like to discuss basic properties of lattice fermions recently well investigated, for example, staggered-Wilson fermion, minimal-doubling fermion and so on.

　

Date/Place 6 Nov. (Tue.) 15:30～ / H711
Name Taro Kimura (RIKEN)
Title Matrix models for Seiberg-Witten theory (slides)
Abstract In this talk we would like to show a matrix model is naturally arising from Nekrasov's instanton partition function for N = 2 gauge theory, and provides Seiberg-Witten curve as the corresponding spectral curve. Not only the standard Hermitian matrix model, but some generalized versions of matrix models are obtained from the gauge theory partition function. In particular we deal with the matrix model corresponding to the instanton counting on orbifold. We will also show that the root of unity limit of the q-deformed partition function plays a crucial role on the orbifolding procedure.
Refs [1] T. Kimura, JHEP 1109 (2011) 015 [arXiv:1105.6091]; Prog. Theor. Phys. 127 (2012) 271-285 [arXiv:1109.0004].

　

Date/Place 30 Oct. (Tue.) 15:00～ / H711
Name Kazunori Kohri (KEK)
Title Determination of neutrino mass hierarchy by 21 cm line and CMB B-mode polarization observations (slides)
Abstract We focus on the ongoing and future observations for both the 21 cm line and the CMB B-mode polarization produced by a CMB lensing, and study their sensitivities to the effective number of neutrino species, the total neutrino mass, and the neutrino mass hierarchy. We find that combining the CMB observations with future square kilometer arrays optimized for 21 cm line such as Omniscope can determine the neutrino mass hierarchy at a 95 \% C.L.

　

Date/Place 23 Oct. (Tue.) 15:30～ / H711
Name Shota Komatsu (Tokyo U.)
Title Three-point functions in N=4 super Yang-Mills from integrability (slides)
Abstract N=4 super Yang-Mills is a 4-d supersymmetric gauge theory, relevant to the best studied example of AdS/CFT duality. Two- and three-point functions of this theory are of extreme importance in two respects. First, as the theory is conformal, two- and three-point functions determine all the other correlation functions. Second, under AdS/CFT duality, these two quantities (are believed to) describe the motion of a string and the interaction of strings respectively. As for two point functions, it is known that the perturbative calculation of the gauge theory can be mapped to a 1-d spin chain. Furthermore, an exact answer, valid at any coupling constant, was proposed a few years ago utilizing the techniques called integrability. In this talk, after overviewing the calculation of two-point functions, I will discuss the recent development on three-point functions, first briefly from the gauge theory side and then in detail from the string theory side based on our works.

　

Date/Place 16 Oct. (Tue.) 15:30～ / H711
Name Akira Ohnishi (Kyoto U.)
Title Auxiliary field Monte-Carlo study of the QCD phase diagram at strong coupling (slides)
Abstract We study the QCD phase diagram at strong coupling by using a newly developed method, auxiliary field Monte-Carlo (AFMC). In the strong coupling lattice QCD, we obtain the effective action at a given order of 1/g^2. In many of previous works, mean-field approximation has been applied to obtain the phase diagram. There are several exceptions which invoke the monomer- dimer-polymer (MDP) simulation and include fluctuation effects in the strong coupling limit [1], but it is not straightforward to extend of the MDP simulation to take account of finite coupling effects. In AFMC, we integrate out the auxiliary field exactly by using the Monte-Carlo technique. Since effective actions with finite coupling effects (1/g^2,1/g^{2Nτ}) have been obtained and their bosonized versions have been known to work well under the mean field approximation [2], it would be straightforward to include fluctuation effects in those auxiliary field effective actions. While we have the sign problem in AFMC, we find that there is a cancellation mechanism of the phase for low momentum auxiliary field and the average sign factor is around cosθ~0.9 for a small lattice such as 4^4. In the presentation, we discuss how we can obtain the effective action in the strong coupling lattice QCD, and present some of our recent results on the QCD phase diagram.
Refs [1] F. Karsch, K.-H. Mutter, Nucl. Phys. B313(1989)541; P. de Forcrand, M. Fromm, Phys. Rev. Lett. 104 (2010) 112005.
[2] T. Z. Nakano, K. Miura, A. Ohnishi, Phys.Rev. D83 (2011) 016014; K. Miura, T.Z. Nakano, A. Ohnishi, N. Kawamoto, Phys.Rev. D80 (2009) 074034

　

Date/Place 9 Oct. (Tue.) 15:30～ / H711
Name Hiroyuki Fuji (Nagoya U.)
Title Asymptotic behavior of the colored superpolynomial
Abstract In this talk, I would like to discuss the homological knot invariant. The knot invariants and QFT is intimately related via the Chern-Simons gauge theory. In recent years, the 2-parameter refinement of the Chern-Simons gauge theory is developed remarkably. The Wilson loop expectation value of the refined Chern-Simons theory is studied for various knot diagrams, and such physical amplitude gives the superpolynomial which is defined mathematically as the homological knot invariants. In a series of collaborations with S. Gukov, M. Stosic, and P. Sulkowski, we studied the asymptotic behavior of the homological knot invariants, and introduced a new knot invariant that we call it as super-A-polynomial. In this talk, I would like to explain about the elementary aspects of homological invariant and asymptotic behavior of the knot invariant.

　

Date/Place 2 Oct. (Tue.) 15:00～ / H711
Name Shinji Ejiri (Niigata U.)
Title Toward the understanding of QCD phase structure at high temperature and density (slides)
Abstract Numerical simulations of Lattice QCD are the most powerful method to study QCD. However, when one tries to investigate at finite density, one encounters serious difficulties. Because the quark determinant is a complex number at finite density, the Monte-Carlo method cannot be applied directly. Among methods to avoid the problem of the complex determinant, we explain a reweighting method focusing on probability distribution functions in this talk. We try to solve the problems which arise in the finite density QCD, i.e. the sign problem and the overlap problem, using this method. After discussing general properties of the probability distribution function, we investigate the critical point which separates the first order transition and crossover, expected in the high density region.

　

Date/Place 9 Aug. (Thu.) 15:00～ / H711
Name Masaki Asano (Hamburg U)
Title Naturalness in SUSY models and LHC results
Abstract Current results of LHC experiments exclude large area of light new particle region, namely natural parameter space, in SUSY models. One of the possibilities for achieving the correct electroweak symmetry breaking naturally is low scale messenger scenario. In this talk, we discuss the constraints and allowed mass spectrum in SUSY models which realizes the natural electroweak symmetry breaking (based on arXiv:1204.0508).

　

Date/Place 31 Jul. (Tue.) 13:00～ / H711
Name Kenji Nishiwaki (Harish-Chandra Research Institute)
Title Non-minimal Universal Extra Dimensions: The strongly interacting sector at the Large Hadron Collider (slides)
Abstract We work out the strongly interacting sector of a non-minimal Universal Extra Dimension scenario with one flat extra spatial dimension orbifolded on S1/Z2 in the presence of brane-localized kinetic and Yukawa terms. On compactification, these terms are known to have significant, nontrivial impact on the masses and the couplings of the Kaluza-Klein (KK) excitations. We study the masses of the level 1 KK gluon and the quarks and find the modified strong interaction vertices involving these particles. The scenario conserves KK parity. Possibility of significant level-mixing among the quarks from different KK-levels is pointed out with particular reference to the top quark sector. Cross sections for various generic final states involving level 1 KK-gluon and KK-quarks from first two generations are estimated at the Large Hadron Collider (LHC) via an implementation of the scenario in MadGraph-5 with the help of FeynRules. Nuances of the scenario are elucidated with reference to the minimal Universal Extra Dimension and Supersymmetry and their implications for the LHC are discussed.
Reference: AseshKrishna Datta, Kenji Nishiwaki, and Saurabh Niyogi, " Non-minimal Universal Extra Dimensions: The strongly interacting sector at the Large Hadron Collider ", [arXiv:1206.3987 [hep-ph]].

　

Date/Place 31 Jul. (Tue.) 15:00～ / H711
Name C.S. Lim (Kobe U)
Title Anomalous Interactions in Gauge-Higgs Unification (slides)
Abstract In the scenario of gauge-Higgs unification, Higgs originates from higher dimensional gauge field and has a physical meaning as AB phase or Wilson loop. As its inevitable consequence, physical observables are expected to be periodic in the Higgs field and the Higgs interactions with fermion is expected to show non-linear behavior. On the other hand, the Yukawa coupling is originally provided by gauge interaction, which is linear in the Higgs field. We discuss how such two apparent contradiction can be reconciled in the simplest framework of the scenario: SU(3) electroweak model in 5-dimensional flat space-time with orbifolding. We also discuss that the gauge interactions of W and Z with fermions show anomalous behavior.

　

Date/Place 17 Jul. (Tue.) 13:00～ / H711
Name Mitsutoshi Fujita (Washington U)
Title SL(2,Z) Action on AdS/BCFT and Hall conductivities (slides)
Abstract We study the response of a conserved current to external electromagnetic fields in a holographic system with boundaries using the recently proposed AdS/BCFT (boundary conformal field theory) framework. This, in particular, allows us to extract the Hall current, the Hall conductivity, plus some potentially novel transport coefficients, and relations among them. We also analyze the action of SL(2,Z) duality in the gravity bulk, which acts non-trivially on the conductivity of the BCFT. Finally we consider a type IIA string theory embedding of our setup.

　

Date/Place 17 Jul. (Tue.) 15:00～ / H711
Name Yosuke Imamura (Tokyo Tech)
Title Dualities in lens spaces
Abstract The partition functions of supersymmetric field theories in various Euclidean backgrounds were recently obtained exactly. They are in general complex, and it is difficult to determine their phases unambiguously. In this talk, I will introduce a way to fix the phase factors of the partition functions of theories in lens spaces with the help of dualities between field theories.

　

Date/Place 10 Jul. (Tue.) 15:00～ / H711
Name Jason Doukas (NII)
Title Localized detection of the Unruh effect: Entanglement degradation across the horizon
Abstract The Unruh effect is a fundamental result of the application of quantum field theory to curved spacetimes. It states that accelerated observers experience the vacuum as a thermal state of particles at a temperature proportional to the acceleration. The subject of the Unruh effect has received renewed interest in the last decade, as the quantum optics community have begun to realize that the Unruh transformation is an example of a basic and well-known class of Gaussian unitary operations known as two-mode squeezing operations. Two mode squeezed vacuum states, are entangled states that are generated by parametric-down conversion in non-linear crystals. It has been the focus of the newly emerging field of Relativistic Quantum Information theory to characterize how this squeezing operator in conjunction with the existence of event horizons can degrade the entanglement that accelerated observers observe. However, all previous models suffered from a misinterpretation of the dependence of the entanglement on the choice of initial state, which was incorrectly attributed to the acceleration. This misinterpretation can be traced back to the use of global field modes like Unruh modes, where the inability to control the size and location of their observation left the physical interpretation of these models unclear. In this talk I will discuss a recent series of works I have done in collaboration, which re-investigates the problem of entanglement degradation due to acceleration in a completely localized setting. I will discuss how the approach enables one for the first time to solve the acceleration degradation problem and leads to new insights into the degradation process.

　

Date/Place 3 Jul. (Tue.) 15:00～ / H711
Name Shin Nakamura (Kyoto U)
Title Nonequilibrium Phase Transitions and Nonequilibrium Critical Point from AdS/CFT (slides)
Abstract We find novel phase transitions and critical phenomena that occur only outside the linear-response regime of current-driven nonequilibrium states. We consider strongly-interacting (3+1)-dimensional N=4 large-Nc SU(Nc) supersymmetric Yang-Mills theory with a single flavor of fundamental N=2 hypermultiplet as a microscopic theory. We compute its nonlinear non-ballistic quark-charge conductivity by using the AdS/CFT correspondence. We find that the system exhibits a novel nonequilibrium first-order phase transition where the conductivity jumps and the sign of the differential conductivity flips at finite current density. A nonequilibrium critical point is discovered at the end point of the first-order regime. We propose a nonequilibrium-steady-state analogue of thermodynamic potential in terms of the gravity-dual theory in order to define the transition point. Nonequilibrium analogues of critical exponents are proposed as well. Critical behaviors of the conductivity are numerically confirmed based on these proposals. The present work provides a new example of nonequilibrium phase transitions and nonequilibrium critical points. Reference: arXiv:1204.1971 [hep-th]

　

Date/Place 26 Jun. (Tue.) 15:00～ / H711
Name Yuji Okawa (Tokyo U, Komaba)
Title Gauge fixing of open superstring field theory in the Berkovits formulation (slides)
Abstract We discuss gauge fixing of the free open superstring field theory in the Berkovits formulation. We determine the world-sheet quantum numbers of all ghost and antighost string fields which appear in the process of gauge fixing and derive propagators in a simple class of gauges. We also discuss the relation to open superstring field theory in the Witten formulation and the construction of the master action in the Batalin-Vilkovisky formalism for the interacting theory.

　

Date/Place 12 Jun. (Tue.) 15:00～ / H711
Name Masaki Yang (U of Tokyo)
Title Recent improvements in the evaluation of neutron electric dipole moment (slides)
Abstract The electric dipole moments (EDMs) are sensitive to a new CP violating source, and become good probes to search New physics. Then, many measurements of EDM are done so far and still planning now. In this seminar, we review experimental condition and theoretical circumstance of EDMs. After that, we present our recent studies about improvements in the QCD corrections of the neutron EDM.

　

Date/Place 5 Jun. (Tue.) 15:00～ / H711
Name Satoshi Yamaguchi (Osaka U)
Title Holographic interface (slides)
Abstract We consider two N=4 supersymmetric gauge theories connected by an interface and the gravity dual of this system. This interface is expressed by a fuzzy funnel solution of Nahm's equation in the gauge theory side. The gravity dual is a probe D5-brane in AdS_5 x S^5. The potential energy between this interface and a test particle is calculated in both the gauge theory side and the gravity side by the expectation value of a Wilson loop. We also consider the expectation values of chiral primary operators in the presence of the interface. We show the gauge theory result and the gravity one agree with each other for both quantities.

　

Date/Place 29 May. (Tue.) 15:00～ / H711
Name Yasuaki Hikida (Keio U)
Title Higher spin AdS_3 supergravity and its dual CFT
Abstract Gravity theory is a gauge theory of spin 2 field, and it is possible to construct gauge theories of higher spin fields with non-trivial interactions if defined on AdS space. Recently, Gaberdiel and Gopakumar conjectured that a large N minimal model is dual to a bosonic subsector of a higher spin supergravity on 3d AdS space by Prokushkin and Vasiliev. Here we propose a supersymmetric version of the duality, where N=(2,2) CP_N Kazama-Suzuki model is dual to the full higher spin supergravity theory. We give strong evidences which support our conjecture. [Ref. JHEP1202(2012)109]

　

Date/Place 22 May. (Tue.) 15:00～ / H711
Name Prof. Morimitsu Tanimoto (Niigata U)
Title Squark flavor mixing and CP violations of B mesons
- B meson Physics in the LHC Era - (slides)
Abstract LHCb provides chances to find new physics in the B meson decays. In this seminar, I outline the B meson physics in the LHC Era. And then, we present our recent works, in which squark flavor mixing contributes to the CP violations of B mesons. LHCb and Bell II give us the good test for the new physics models.

　

Date/Place 15 May. (Tue.) 15:00～ / H711
Name Masazumi Honda (Sokendai)
Title Localization and Large N reduction on S^3 for the Planar and M-theory limit
Abstract We show a large N reduction on S^3 in a BPS sector for a broad class of theories : N>=2 supersymmetric Chern-Simons theory with any number of adjoint and bi-fundamental chiral multiplet. We show that the localization method can be applied to the reduced model and the path integral can be written by multi-contour integral. By taking particular localization configuration, we also show that the large N equivalence between the original theory on S^3 and the reduced model holds for the free energy and for the expectation value of BPS Wilson loops. It turns out that the large N reduction on $S^3$ holds even for the M-theory limit.

　

Date/Place 8 May. (Tue.) 15:00～ / H711
Name Dr. Jong-Wan Lee (KEK)
Title Lattice study of unitary fermions (slides)
Abstract In this seminar, I will talk about a recently developed lattice Monte Carlo method to study large systems of strongly interacting non-relativistic two-component fermions at zero temperature, and its application to a dilute gas of fermions near unitarity. The systematic errors associated with finite lattice spacings and finite volumes will be discussed in detail along with a highly improved lattice action. I will also discuss an overlap problem appearing in the form of heavy-tailed many-body correlator distributions and propose a new statistical technique for extracting ground state energies in such systems.

　

Date/Place 1 May. (Tue.) No Seminar due to the school holiday
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Date/Place 24 Apr. (Tue.) 15:00〜 / H711
Name Dr. Yuta Orikasa (Osaka U)
Title The classically conformal B-L extended standard model(slides)
Abstract Under a hypothesis of classically conformal theories, we investigate the minimal B-L extended Standard Model, which naturally provides the seesaw mechanism for explaining tiny neutrino masses. In this setup, electroweak symmetry breaking is triggered by radiative B-L symmetry breaking. The model naturally predicts TeV scale B-L breaking as well as a light standard-model singlet Higgs boson and right-handed neutorinos around the same energy scale. In this model, the baryogenesis is realized thorough the resonant leptogenesis. I found that a fixed CP-phase can simultaneously reproduce all neutrino oscillation data and the observed baryon asymmetry in the present Universe.

　

Date/Place 17 Apr. (Tue.) 15:00〜 / H711
Name Dr. Ryo Takahashi (Osaka U)
Title Split seesaw mechanism and flavor symmetry(slides)
Abstract A seesaw mechanism in an extra-dimension, known as the split seesaw mechanism, provides a natural way to realize a splitting mass spectrum of right-handed neutrinos. It leads to one keV sterile neutrino as a dark matter candidate and two heavy right-handed neutrinos being responsible for leptogenesis to explain the observed baryon asymmetry of the Universe. We study models based on A4 flavor symmetry in the context of the split seesaw mechanism. It is pointed out that most of known A4 flavor models with three right-handed neutrinos being A4 triplet suffer from a degeneracy problem for the bulk mass terms, which disturbs the split mechanism for right-handed neutrino mass spectrum. Then we construct a new A4 flavor model to work in the split seesaw mechanism. The model can be consistent with all data of neutrino oscillation experiments, cosmological discussions of dark matter abundance, leptogenesis, and recent astrophysical data.

　

Date/Place 9 Apr. (Mon.) 15:30〜 / H711
Name Dr. Dongming Gang (KIAS, Korea)
Title Line Operator Index on S1 $\times$ S3(slides)
Abstract We derive a general formula of an index for N = 2 superconformal field theories on S1 \times S3 with insertions of BPS Wilson line or 't Hooft line operator at the north pole and their anti-counterpart at the south pole of S3. One-loop and monopole bubbling effects are taken into account in the computation. As examples, we calculate the indices for N = 4 theories and N = 2 SU(2) theory with Nf = 4, and find good agreements between indices of line operators related by S-duality. The relation between Verlinde loop operators and the indices is explored. The holographic correspondence between the fundamental (anti-symmetric) Wilson line operator and the fundamental string (D5 brane) in AdS5\timesS5 is confirmed by the index comparison.

　

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