Backnumber 2013

Back Numbers 2013-14 Back to Home (Japanese) Back-Numbers etc.

DAY & TIME : 2/28 (Fri.) 10:30-12:00
SPEAKER : D. Kadoh (KEK)
TITLE : An Introduction to Lattice Supersymmetry
ABSTRACT : I introduce recent development of lattice supersymmetry to students and non-experts of lattice field theory.
COMMENT : Morning Seminar

DAY & TIME : 13:30-
TITLE : Gauge/gravity duality from lattice simulation
ABSTRACT : In this talk, I discuss the gauge/gravity duality from lattice simulation of one-dimensional Yang-Mills theory with 16 supercharges. This gauge theory is expected to be dual to N D0-brane system in type IIA superstring theory, based on the duality.
In particular, at finite temperature, low temperature regions in the large N limit correspond to a classical black hole. We calculate the internal energy of the black hole from the gauge theory side using the lattice simulation. Comparing it with an analytic solution of the gravity side, we examine whether the duality is correct.
E-PRINT : D. Kadoh and S. Kamata, "Lattice simulation of lower dimensional SYM with sixteen supercharges," PoS LATTICE 2013: 343
COMMENT : Afternoon Seminar

DAY & TIME : 2/21 (Fri.)
COMMENT : No seminar

DAY & TIME : 2/14 (Fri.) 13:30-15:00, 15:15-16:45
SPEAKER : M. Aoki (Kanazawa Univ.)
TITLE : Multicomponent dark matter in a radiative seesaw model
ABSTRACT : We propose a radiative seesaw model, in which tiny neutrino masses are generated at the two-loop level.
The lepton number is softly broken by a dimension two operator. The tree-level Dirac mass is forbidden by $Z_2 \times Z_2'$, which predicts the existence of two or three dark matter particles. The model is a slight extension of the Ma model (E. Ma, PRD73 (2006) 077301). We show how the allowed parameter space, obtained in the Ma model, changes. Observation prospects of the multicomponent dark matter system will be also discussed.
COMMENT : Seminar

日時： 2014年2月12日（木）15:00-
場所：２号館 2-402
講師：金谷奈央子　（東京大学素粒子物理国際センター）
題目： Results and prospect of SUSY searches at the LHC
要旨： LHC実験は2012年12月に重心系エネルギー８TeVでの陽子-陽子衝突実験を無事に終了させ 1実験あたり約20 fb^-1のデータを蓄積した。全データを用いたSUSY探索の解析結果と高ルミノシティランでの展望についてお話したいと思います。

DAY & TIME : 2/7 (Fri.)
COMMENT : No seminar

DAY & TIME : 1/31 (Fri.) 10:30-12:30
SPEAKER : Y. Yamaguchi (Hokkaido Univ.)
TITLE : ニュートリノフィリック・ヒッグス模型における熱的レプトジェネシス
SPEAKER : K. Nakagawa (Hokkaido Univ.)
TITLE : 3次元時空における物質場と相互作用する高階スピン重力理論のAdS/CFT対応
SPEAKER : K. Koyama (Hokkaido Univ.)
TITLE : スカラー二体崩壊における有限サイズ効果
SPEAKER : N. Shimode (Hokkaido Univ.)
TITLE : Generalised Gauge Theory and Higher Spin Algebra -- an introduction --
SPEAKER : S. Nakano (Hokkaido Univ.)
TITLE : The Prospect of Neutralino Dark Matter Search in Minimal Supersymmetric Model
COMMENT : Short Rehearsal of Master Thesis Presentation

DAY & TIME : 1/31 (Fri.) 13:30-
SPEAKER : N. Yokomakura (Hokkaido Univ.)
TITLE : Palatini Theory of Gravity
E-PRINT : G. J. Olmo, "Palatini Approach to Modified Gravity: f(R) Theories and Beyond," arXiv:1101.3864v1[gr-qc],
G. J. Olmo, "Cosmology in Palatini theories of gravity," arXiv:1207.4815v1[gr-qc],
G. J. Olmo, P. Singh, "Covariant Effective Action for Loop Quantum Cosmology a la Palatini," arXiv:0806.2783v2[gr-qc]
COMMENT : Journal Club

DAY & TIME : 1/24 (Fri.) 10:30-12:30, 13:30-
SPEAKER : K. Koyama (Hokkaido Univ.)
TITLE : Two body decay with finite size correction
SPEAKER : N. Shimode (Hokkaido Univ.)
TITLE : On Possible Extensions of Gauge theory
ABSTRACT : Possible ways of extending gauge theory are described. A review on what the authors (Kawamoto and Watabiki) call "generalised gauge theory", and a study of its mathematical structure are given.
E-PRINT : N. Kawamoto and Y. Watabiki, Mod. Phys. Lett. A 07, 1137-1147 (1992),
N. Kawamoto, Y. Watabiki, Comm. Math. Phys. 144, 641-648 (1992)
SPEAKER : S. Nakano (Hokkaido Univ.)
TITLE : The prospect of dark matter direct detection in mSUGRA with mh=125GeV
ABSTRACT : The recent LHC measurement of the Higgs mass ~ 125 GeV highly constraints on the dark matter relic density and also the well known benchmark regions in mSUGRA parameter space. In my talk, I will present updated features of Neutralino dark matter in parameter scan of mSUGRA with m_h~125GeV. In addition, the simulation results will be compared with the latest experimental data.
COMMENT : Long Rehearsal of Master Thesis Presentation

DAY & TIME : 1/17 (Fri.) 10:30-12:30
SPEAKER : Y. Yamaguchi (Hokkaido Univ.)
TITLE : Detailed renormalization group analysis for light neutrino mass matrix
ABSTRACT : We consider renormalization group equations of light neutrino mass matrix with the SM particle decouplings, and show the differences whether the decouplings are considered or not. In our study, the light neutrino masses are described by an effective five dimension operator, called Weinberg operator. We find the differences for mixing angles are negligible, but the differences for mass eigenvalues are not. And, we discuss the dependence on mass spectrum of light neutrinos, degeneracy of light neutrino masses and CP-phases.
SPEAKER : K. Nakagawa (Hokkaido Univ.)
TITLE : AdS/CFT and 3D Higher-Spin Gauge Theory
ABSTRACT : Higher spin gauge theory is thought as a toy model of string theory. An influential candidate is Vasiliev theory, which is thought AdS/CFT correspondence already. However, nobody knows the action. In my talk, I review AdS/CFT correspondence and 3D Vasiliev theory, and propose the action that gives the appropriate AdS/CFT correspondence at the linearized equation level.
COMMENT : Long Rehearsal of Master Thesis Presentation

DAY & TIME : 1/17 (Fri.) 13:30-
SPEAKER : T. Kobayashi (Kyoto Univ.)
TITLE : Phenomenological aspects of magnetized brane models
ABSTRACT : 背景磁場をもつコンパクト空間の現象論的性質を議論する。世代数、ゼロモード波動関数、湯川結合、フレーバー対称性など４次元低エネルギー有効理論の様々な性質をまとめ、現実的な模型の構成を議論する。
COMMENT : Seminar

DAY & TIME : 1/10 (Fri.) 10:30-12:00
SPEAKER : Y. Tobita (Hokkaido Univ.)
TITLE : Restricting the LSND and MiniBooNE sterile neutrinos with the IceCube atmospheric neutrino data
E-PRINT : A. Esmaili, A. Yu. Smirnov, "Restricting the LSND and MiniBooNE sterile neutrinos with the IceCube atmospheric neutrino data," [arXiv:1307.6824]
COMMENT : Journal Club

DAY & TIME : 1/10 (Fri.) 13:30-
SPEAKER : K. Hotta (Hokkaido Univ.)
TITLE : Brane-Antibrane at Finite Temperature in the Framework of Thermo Field Dynamics
ABSTRACT : Previously we have investigated the thermodynamical properties of brane-antibrane pairs by calculating the one-loop free energy and the finite temperature effective action in the framework of Matsubara formalism. This calculation is based on boundary string field theory, and we have a problem of a choice of Weyl factors on the two boundaries of one-loop open string worldsheet. We have chosen one of them, and compute the one-loop free energy. In this paper, we compute the thermal vacuum state and the partition function for a single open string on a brane-antibrane pair in the framework of thermo field dynamics. From this we can reproduce the free energy for multiple strings in the case of Matsubara method. This implies that our choice of Weyl factors in the previous work is quite natural.
COMMENT : Seminar

DAY & TIME : 12/20 (Fri.) 11:00-12:00
SPEAKER : Y. Toda (Hokkaido Univ.)
TITLE : The Dimension of Quantized Bosonic String
E-PRINT : P. Goddard, J. Goldstone, C. Rebbi, C. B. Thorn, "Quantum dynamics of a massless relativistic string," Nucl. Phys. B56 (1973) 109
SPEAKER : H. Hattori (Hokkaido Univ.)
TITLE : QEDによるLamb shiftの計算について
REFERENCE : S. S. Schweber, "QED and the man who made it: Dyson, Feynman, Schwinger, and Tomonaga"
COMMENT : M1 Journal Club Rehearsal

DAY & TIME : 12/13 (Fri.) 10:30-12:00
SPEAKER : K. Suehiro (Hokkaido Univ.)
TITLE : Inplications of Higgs Discovery for the MSSM
E-PRINT : A. Djouadi, "Implications of the Higgs discovery for the MSSM," [arXiv:1311.0720[hep-ph]]
E. Hardy, "Heavy superpartners with less tuning from hidden sector renormalisation," [arXiv:1311.2944[hep-ph]]
COMMENT : Journal Club

DAY & TIME : 12/13 (Fri.) 13:30-
SPEAKER : M. Aiba (Hokkaido Univ.)
TITLE : Renormalization of gravity and its higher-derivative extension
PAPER : K. S. Stelle, "Renormalization of higher-derivative quantum gravity," Phys. Rev. D 16, 953-969 (1977)
SPEAKER : W. Akutsu (Hokkaido Univ.)
TITLE : The Higgs mechanism and the Glashow-Weinberg-Salam Theory
PAPER : S. Weinberg, "A Model of Leptons," Phys. Rev. Lett. 19:1264-1266(1967),
P. W. Higgs, "Broken symmetries, massless particles and gauge fields," Phys.Lett. 12 (1964) 132-133,
F. Englert and R. Brout, "Broken Symmetry and the Mass of Gauge Vector Mesons," Phys. Rev. Lett. 13, 321-323(1964)

SPEAKER : Y. Takano (Hokkaido Univ.)
TITLE : Scale and conformal invariance in field theory
PAPER : J. Polchinski, "Scale and conformal invariance in quantum field theory," Nucl. Phys. B303 (1988) 226
COMMENT : M1 Journal Club Rehearsal

DAY & TIME : 12/6 (Fri.) 10:30-12:00, 13:30-
SPEAKER : S. Shiba (KEK)
TITLE : Thermodynamics of black branes from effective field theories
ABSTRACT : We consider a model of D-dimensional supergravity coupled to elementary p-branes, and write down the leading terms for the low energy classical effective theory of N nearly coincident branes that are weakly gravitationally interacting. This takes the form of a local scalar field theory in (p+1)-dimensions, where the scalars represent the positions of the branes in their transverse space. We propose that the same theory at finite temperature describes a `soup' of strongly interacting branes, which provides a microscopic description of near extremal supergravity black p-branes.
Especially, in D=11 case, we can discuss the thermodynamics of black M-branes in terms of field theory. We show that the free energy with exotic N-dependence, obtained from supergravity, can be properly reproduced. This result seems to justify our discussion.
E-PRINT : T. Morita and S. Shiba,"Thermodynamics of black M-branes from SCFTs," JHEP 1307 (2013) 100, [arXiv:1305.0789[hep-th]].
T. Morita, S. Shiba, T. Wiseman and B. Withers, "Warm p-soup and near extremal black holes," [arXiv:1311.6540[hep-th]].
COMMENT : Seminar

DAY & TIME : 11/29 (Fri.) 10:30-12:00
SPEAKER : E. Park (Hokkaido Univ.)
TITLE : LHC constraints on light neutralino dark matter in the MSSM
E-PRINT : G. Belanger, G. D. La Rochelle, B. Dumont, R. M. Godbole, S. Kraml, S. Kulkarni, "LHC constraints on light neutralino dark matter in the MSSM," [arXiv:1308.3735]
COMMENT : Journal Club

DAY & TIME : 11/22 (Fri.) 10:30-12:00, 13:30-
SPEAKER : Y. Hikida (Rikkyo Univ.)
TITLE : Higher spin fields, strings and AdS/CFT
ABSTRACT : Higher spin gauge theory can be thought as a toy model of string theory, and it attracts a lot of attention recently due to the application for AdS/CFT correspondence. A famous example is the duality between a 4d higher spin gauge theory and 3d O(N) vector model. 3d higher spin gauge theory is also supposed to be dual to a large N minimal model. We are interested in the latter case since lower dimensional theories are more tractable in general. Recently it was proposed that a 4d higher spin gauge theory with matrix valued fields is dual to Aharony-Bergman-Jafferis (ABJ) theory. Since ABJ theory is known to be dual to a superstring theory, this duality implies a non-trivial relation between higher spin gauge theory and superstring theory. In this talk, we propose that a similar type of 3d higher spin theories are dual to 2d Grassmannian-like models, and we give supports for the conjecture. We would like to discuss possible relations to superstring theory.
E-PRINT : T. Creutzig, Y. Hikida, P. B. Ronne, "Extended higher spin holography and Grassmannian models," [arXiv:1306.0466]
COMMENT : Seminar

DAY & TIME : 11/15 (Fri.) 10:30-12:00
SPEAKER : R. Nakayama (Hokkaido Univ.)
TITLE : BMS and Holographic Reduction of Minkowski Spacetime
E-PRINT : G. Barnich and P-H. Lambert, "Einstein-Yang-Mills theory: I. Asymptotic symmetries," [arXiv:1310.2698]
Andrew Strominger, "Asymptotic Symmetries of Yang-Mills Theory," [arXiv:1308.0589]
J. de Boer and S.N. Solodukhin, "A Holographic Reduction of Minkowski Spacetime," [arXiv:hep-th/0303006]
COMMENT : Journal Club

DAY & TIME : 11/8 (Fri.) 10:30-12:00
SPEAKER : M. Jinzenji (Hokkaido Univ.)
TITLE : Multi-Point Virtual Structure Constants and Mirror Computation of CP^2-model
ABSTRACT : In this paper, we propose a geometrical approach to mirror computation of genus 0 Gromov-Witten invariants of CP^2. We use multi-point virtual structure constants, which are defined as intersection numbers of a compact moduli space of quasi maps from CP^1 to CP^2 with 2+n marked points. We conjecture that some generating functions of them produce mirror map and the others are translated into generating functions of Gromov-Witten invariants via the mirror map. We generalize this formalism to open string case. In this case, we have to introduce infinite number of deformation parameters to obtain results that agree with some known results of open Gromov-Witten invariants of CP^2. We also apply multi-point virtual structure constants to compute closed and open Gromov-Witten invariants of a non-nef hypersurface in projective space. This application simplifies the computational process of generalized mirror transformation.
E-PRINT : M. Jinzenji, M. Shimizu, "Multi-Point Virtual Structure Constants and Mirror Computation of CP^2-model," [arXiv:1305.0999]
COMMENT : Morning Seminar

DAY & TIME : 11/1 (Fri.) 10:30-12:00
SPEAKER : N. Kawamoto (Hokkaido Univ.)
TITLE : Higher-Spin Gauge Theories for Gravity
E-PRINT : M. Vasiliev, "Higher-Spin Gauge Theories in Four, Three and Two Dimensions," [arXiv:hep-th/9611024]
M. A. Vasiliev, "Actions, Charges and Off-Shell Fields in the Unfolded Dynamics Approach," [arXiv:hep-th/0504090]
X. Bekaert, S. Cnockaert, C. Iazeolla, M. A. Vasiliev, "Nonlinear higher spin theories in various dimensions," [arXiv:hep-th/0503128]
COMMENT : Journal Club

DAY & TIME : 10/25 (Fri.) 10:30-12:00, 13:30-
SPEAKER : E. Senaha (Nagoya Univ.)
TITLE : Z'-ino-driven Electroweak Baryogenesis
ABSTRACT : In my talk in the morning, I will give a pedagogical review of electroweak baryogenesis. In particular, I will focus on the sphaleron decoupling condition and the 1st-order electroweak phase transition in the SM and MSSM. Then I will discuss the feasibility of electroweak baryogenesis in the U(1)'-extended MSSM in light of the recently observed 126 GeV Higgs boson in the afternoon. The baryon asymmetry is estimated in a specific scenario in which a Z'-ino plays an essential role in generating the CP-violating source term. Finally, I will give a brief summary and outlook.
E-PRINT : E. Senaha, "Z'-ino-driven Electroweak Baryogenesis in the UMSSM," Phys.Rev. D88 (2013) 055014 [arXiv:1308.3389]
COMMENT : Seminar

DAY & TIME : 10/18 (Fri.) 10:30-12:00
SPEAKER : V. Kazakov (École Normale Supérieure)
TITLE : Solving (exactly) a 4-dimensional gauge theory
ABSTRACT : I will review recent progress in solving exactly, in planar limit, a non-trivial 4-dimensional gauge theory - the N=4 Super-Yang-Mills (SYM) theory. This theory is the most notorious example of the famous AdS/CFT correspondence between a SYM theory and a superstring sigma model on a non-trivial background. An additional important property of this duality - the integrability, has allowed the formulation of exact equations for anomalous dimensions of operators in this quantum conformal field theory. These equations allow for an efficient strong and weak coupling (currently up to 9 orders in perturbation theory!) expansions, as well as for very precise numerical computation of dimensions, at any relevant strength of the coupling. I will discuss the basics of the integrability approach to this system.
COMMENT : Morning Seminar
DAY & TIME : 10/18 (Fri.) 13:30-
SPEAKER : V. Kazakov (École Normale Supérieure)
TITLE : Integrability of spectrum of N=4 SYM theory
ABSTRACT : Following the content of my first talk, I will explain the state of art of calculations of spectrum of anomalous dimensions in N=4 SYM. It culminates in a system of exact, at any coupling, Riemann-Hilbert-type equations for the spectral curve of the problem. A few examples of calculation of anomalous dimensions for particular operators will be given.
COMMENT : Afternoon Seminar

DAY & TIME : 10/18 (Fri.) 15:30-16:00
SPEAKER : N. Shimode (Hokkaido Univ.)
TITLE : カイラル・アノマリー
E-PRINT : K. Fujikawa, Phys. Rev. Lett. 42, 1195-1198(1979), "Path-Integral Measure for Gauge-Invariant Fermion Theories"
COMMENT : M1 Journal Club Rehearsal

DAY & TIME : 10/11 (Fri.) 10:30-12:00, 13:30-
SPEAKER : Y. Matsuo (KEK)
TITLE : A Self-consistent Model of the Black Hole Evaporation
ABSTRACT : We construct a self-consistent model which describes a black hole from formation to evaporation including the back reaction from the Hawking radiation. In the case where a null shell collapses, at the beginning the evaporation occurs, but it stops eventually, and a horizon and singularity appear. On the other hand, in the generic collapse process of a continuously distributed null matter, the black hole evaporates completely without forming a macroscopically large horizon nor singularity. We also find a stationary solution in the heat bath, which can be regarded as a normal thermodynamic object.
E-PRINT : H. Kawai, Y. Matsuo, Y. Yokokura, "A Self-consistent Model of the Black Hole Evaporation," [arXiv:1302.4733]
COMMENT : Seminar

DAY & TIME : 10/4 (Fri.) 10:30-12:00, 13:30-
SPEAKER : K. Murakami (OIQP)
TITLE : Multiloop amplitudes of light-cone gauge bosonic string field theory in noncritical dimensions
ABSTRACT : Superstring field theory has not been established yet, mainly because of a divergence problem called the ``contact term problem", which occurs even at the tree-level. This happens in the light-cone gauge formulation as well as gauge invariant one. In order to deal with this divergence for the light-cone gauge NSR superstring field theory, we have proposed the regularization scheme in which the spacetime dimensions is shifted to a large negative value. So far we have verified that our dimensional regularization works for the tree-level amplitudes. As a first step towards the examination whether the dimensional regularization works for the multiloop amplitudes, we study in this work the multiloop amplitudes of the light-cone gauge closed bosonic string field theory in noncritical dimensions. We show that the amplitudes can be recast into a BRST invariant form by adding a nonstandard worldsheet theory for the longitudinal variables and the reparametrization ghost system.
E-PRINT : N. Ishibashi, K. Murakami, "Multiloop Amplitudes of Light-cone Gauge Bosonic String Field Theory in Noncritical Dimensions," [arXiv:1307.6001]
COMMENT : Seminar

日時： 2013年9月26日（木）16:30-18:00
場所：２号館 2-409
講師：磯　暁　（高エネルギー加速器研究機構教授）
題目：ヒッグス粒子の発見が意味すること
要旨：長年待ち望まれてきたヒッグス粒子が、ついに昨年発見された。その質量126GeVは、電弱相互作用とプランクスケールの物理との間に密接な関係があることを示唆している。この講演では、電弱理論の大きな謎である階層性問題と真空の安定性に注目して、ヒッグス粒子発見の意義、これからの素粒子論の展望についてお話したい。

DAY & TIME : 8/2 (Fri.) 10:30-12:00, 13:30-
SPEAKER : H. Nakano (Nigata Univ.)
TITLE : An R-symmetric extension of SUSY model: neutrino mass and proton stability
ABSTRACT : In the first part, we review some basic properties of supersymmetric models with an emphasis on a possible role of continuous R symmetry. This includes nonrenormalization theorem, supersymmetry breaking, suppression of proton decay and flavor violations. We also discuss the theory of Dirac gaugino and supersoft SUSY breaking.
In the second part, we discuss an R symmetric extension of minimal SUSY standard model, in which SUSY is broken in the Higgs sector in addition to hidden sector. The U(1)_R symmetry in the visible sector is broken by coupling to supergravity, and is parametrized by a small gravitino mass. With a special R charge assignment for right-handed neutrino, the present setup provides a natural realization of neutrinophilic Higgs idea; the small R breaking gives rise to a small neutrino mass even with neutrino Yukawa couplings of order one. We also discuss the constraints from proton stability, Higgs phenomenology and cosmology.
COMMENT :Seminar

DAY & TIME : 7/26 (Fri.) 10:30-12:00
SPEAKER : K. Koyama (Hokkaido Univ.)
TITLE : \mu \to e + \gamma process with Finite size effect
ABSTRACT : Measurement of\mu \to e + \gamma decay process is done for the search of new physics beyond the Standard Model. On the other hand finite-size effect on the decay probability, give a large correction in case the mass of the particle after the decay is small. In this presentation, I will talk about motivation to calculate the decay probability.
E-PRINT :K. Ishikawa, Y. Tobita, "Finite-size corrections to Fermi's golden rule: I Decay rates," [arXiv:1303.4568]
COMMENT : M2 Journal Club

DAY & TIME : 7/26 (Fri.) 13:30-
SPEAKER : Y. Yamaguchi (Hokkaido Univ.)
TITLE : Resonant leptogenesis in the neutrinophilic two Higgs doublet model
ABSTRACT : Right-handed neutrinos are introduced to explain the tiny neutrino masses and baryon asymmetry in the Universe (BAU). If the light neutrino mass spectrum is not degenerate, in order to reproduce the observed values both of tiny neutrino masses and BAU, the mass of the lightest right-handed neutrino is larger than 10^8 GeV, which is independent of the model parameters. This bound can become avoidable when the lightest right-handed neutrino and the second-lightest right-handed neutrino are degenerate, therefore the masses of the two right-handed neutrinos can become TeV scale. But, in this case, the first 9-digit value of two masses must be same. In order to reduce this fine-tuning, we consider a two Higgs doublet model, in which an additional Higgs doublet interacts only with neutrinos. As a result, under some parameter region, the fine-tuning can reduce from 9-digit to 4-digit. I will talk about the above discussion, and finally show our result.
E-PRINT :N. Haba and O. Seto, "Low scale thermal leptogenesis in neutrinophilic Higgs doublet models," [arXiv:1102.2889v1]
N. Haba, O. Seto, and Y. Yamaguchi, "Resonant leptogenesis with mild degeneracy," [arXiv:1305.2484v1]
COMMENT : M2 Journal Club

DAY & TIME : 7/26 (Fri.) 15:00-
SPEAKER : K. A. Schiff Croker (Univ. of Hawai'i at Manoa)
TITLE : Uniqueness of Action in Multimetric Gravity
ABSTRACT : In the setting of Einstein-like gravity with multiple metric tensors, it is argued that the appropriate generalization of universal coupling requires revision to the canonical model-building formalism. In particular, we argue that lack of any physically privileged metric precludes consideration of a single action from which all dynamical fields are determined. We present a vacuum toy two-action model exhibiting mathematical features previously overlooked and exhibit a non-empty solution set. We then apply the toy model to the core/cusp problem of galactic dark matter halos and extract experimental predictions via a successive approximation scheme. In particular, observers bound to a Minkowski metric naturally encounter a pseudo-isothermal sphere profile, while the other metric is found to exponentially inflate to Minkowski spacetime. In addition to quantitative agreement within the Milky Way, we predict a simple algebraic dependence between the previously phenomenological fit parameters core density $\rho_0$ and core radius $R_C$, and exhibit possible temporal damping of the halo density.
COMMENT : Informal Seminar

DAY & TIME : 7/19 (Fri.) 10:30-12:00
SPEAKER : K. Nakagawa (Hokkaido Univ.)
TITLE : AdS/CFT Correspondence
E-PRINT : E. Witten, "ANTI DE SITTER SPACE AND HOLOGRAPHY," [arXiv:hep-th/9802150v2]
R. Klebanov and E. Witten, "AdS/CFT Correspondence and Symmetry Breaking," [arXiv:hep-th/9905104v2]
COMMENT : M2 Journal Club
DAY & TIME : 7/19 (Fri.) 13:30-
SPEAKER : S. Nakano (Hokkaido Univ.)
TITLE : Supersymmetric Dark Matter
E-PRINT : G. Jungman, M. Kamionkowski and K. Griest, "Supersymmetric dark matter," Physics Reports 267(1996)195-373, [arXiv:hep-ph/9506380]
S. P. Martin, "A Supersymmetry Primer," [arXiv:hep-ph/9709356]
COMMENT : M2 Journal Club

DAY & TIME : 7/12 (Fri.) 10:30-12:00, 13:30-
SPEAKER : T. Takimi (Tata Institute)
TITLE : Phase structures of Chern-Simons matter theory on S^2 \times S^1
ABSTRACT : As a new interesting class of AdS/CFT duality, 3d fundamental Chern-Simons matter theories can be dual descriptions of the Vasiliev's theory with higher spin symmetry which might be a strong clue for the quantum gravity. Analogous to the AdS/CFT correspondence between the deconfinement phase transition of large N gauge theory on spheres and the gravitational phase transition involving black-hole nucleation, we would be able to study phase structures of the Vasiliev's theory by elaborating phase structures of the Chern-Simons matter theory. Based on this motivation, I have studied phase structures of Chern-Simons matter theories with fundamental representation. In the fundamental Chern-Simons matter theories, due to the absence of the propagating degree of freedom of the gauge fields and by the topological magnetic flux, we can see new phases with saturated eigenvalue density function, which does not show up in the conventional Yang-Mills theories with the Gross-Witten-Wadia type phase transition.
COMMENT : Seminar

DAY & TIME : 7/5 (Fri.) 10:30-12:00
SPEAKER : H. Suzuki (Hokkaido Univ.)
E-PRINT : Juan Maldacena, Leonard Susskind, "Cool horizons for entangled black holes," [arXiv:1306.0533]
COMMENT : Journal Club

DAY & TIME : 6/28 (Fri.) 10:30-12:00
SPEAKER : E. Ma (University of California Riverside)
TITLE : Understanding Quark Mixing and the 126 GeV particle at the LHC
ABSTRACT : The theoretical problem of quark mixing is reviewed and its explanation in terms a non-Abelian discrete symmetry is proposed. After some discussions on the group theory of $S_3$, I will show how the observed pattern of quark mixing may be understood in terms of two approximate residual $Z_2$ symmetries, based on a model proposed in 2004. I will then show that these same residual symmetries guarantee that there is a light scalar particle in this model which looks very much like (but not exactly equal to) that of the Standard Model. Finally, I will propose a crucial test of this model in the rare decay $B_s \to \tau^+ \mu^-$ with a branching fraction as large as $10^{-7}$, whereas $B_s \to \tau^- \mu^+$ is suppressed further by the factor $(m-\mu/m_\tau)^2$.
COMMENT : Morning Seminar

DAY & TIME : 6/21 (Fri.) 10:30-12:00, 13:30-
SPEAKER : M. Fukuma (Kyoto Univ.)
TITLE : Propagators in nonstationary spacetime and the nonequilibrium-thermodynamics character of de Sitter space
ABSTRACT : This talk consists of two parts.
The first half deals with an issue of defining a vacuum in a curved spacetime with no global timelike Killing vector. We propose to choose as the vacuum the instantaneous ground state at each instant, and develop a framework to calculate various Green's functions for such vacuum.
The second half is an application of the above framework, revealing a nonequilibrium-thermodynamics character of de Sitter space. We first introduce an Unruh-DeWitt detector which is coupled to a scalar field starting in the ground state at a finite past, and write down the master equation for the density matrix of the detector. We show that the density distribution exhibits a relaxation to the Gibbs distribution with the universal relaxation time of half the curvature radius of de Sitter space even when the detector is an ideal detector which can get adjusted to its environment instantaneously. This relaxation time gives the first example of such quantities that are related to nonequilibrium dynamics intrinsic to de Sitter space.
E-PRINT : M. Fukuma, Y. Sakatani and S. Sugishita, [arXiv:1301.7352] "On propagators in de Sitter space,"
[arXiv:1305.0256] "Master equation for the Unruh-DeWitt detector and the universal relaxation time in de Sitter space"
COMMENT : Seminar

DAY & TIME : 6/14 (Fri.) 10:30-12:00, 13:30-
SPEAKER : Y. Fujimoto (Kobe Univ.)
TITLE : Higgs mechanism and flavor structure from point interactions in an extra dimension
ABSTRACT : In the context of a five-dimensional gauge theory with a point interaction, we found that a scalar field can acquire a nonvanishing vacuum expectation value even if the scalar mass square is positive. The vacuum expectation value of the scalar field inevitably depends on the extra dimensional coordinate and the phase diagram has a rich structure. Furthermore, we found that three chiral fermion zero modes appear from a single fermion by introducing several point interactions. In the situation, profiles of chiral fermion zero modes are split and localized in different points of extra dimension. An extra dimensional coordinate-dependent vacuum expectation value of a scalar is useful to explain the fermion mass hierarchy. We find that the forms of mass matrices are strongly restricted by the geometry of an extra dimension and discuss how the flavor structures (mass hierarchy, small quark flavor mixing, large lepton flavor mixing, tiny neutrino mass, etc.) of quarks and leptons are explained in our framework. We also discuss the CP phase in our model.
E-PRINT : Y. Fujimoto, K. Nishiwaki, and M. Sakamoto, "CP phase from twisted Higgs VEV in extra dimension," [arXiv:1301.7253]
Y. Fujimoto, T. Nagasawa, K. Nishiwaki and M. Sakamoto, "Quark mass hierarchy and mixing via geometry of extra dimension with point interactions," Prog. Theor. Exp. Phys. 2013, 023B07 [arXiv:1209.5150]
Y. Fujimoto, T. Nagasawa, S. Ohya and M. Sakamoto, "Phase Structure of Gauge Theories on an Interval," Prog. Theor. Phys. 126 (2011), 841-854 [arXiv:1108.1976]
COMMENT : Seminar

DAY & TIME : 6/7 (Fri.) 10:30-12:00
SPEAKER : K. Hotta (Hokkaido Univ.)
TITLE : Black Hole: Complementarity or Firewalls
E-PRINT : arXiv:1207.3123, arXiv:1304.6483
COMMENT : Journal Club

DAY & TIME : 5/31 (Fri.) 10:30-12:00, 13:30-
SPEAKER : K. Ishikawa (Hokkaido Univ.)
TITLE : Finite-size corrections to Fermi Golden rules
ABSTRACT : Fermi's golden rules (I and II) are well known rules for computing decay rates and scattering cross sections from transition amplitudes at large time interval T and have been applied in many area. They are explained in most textbooks of quantum mechanics　but corrections due to finite value of T have not been studied. T in experiments is much larger than an intrinsic time scale of microscopic system and the finite-size corrections were considered negligible accordingly. However, it is found that is not the case in certain situations. For the finite-size corrections, S[T] that satisfies the boundary condition at T is used instead of the ordinary S-matrix, denoted as S[\infty]. S[T] is constructed with wave packets following LSZ. With S[T], we find that the corrections of the form 1/T appear and become non-negligible in several processes. Especially they become large for light particles such as neutrinos and photons, and are necessary to compare the theory with experiments　and provide new physical quantities. Fermi’s golden rule and its corrections are explained in the introduction, and derivations and various implications of the corrections are given in the seminar.
E-PRINT: arXiv:1303.4568,"Finite-size corrections to Fermi’s golden rule:I Decay rates," Ishikawa and Tobita, (PTEP to appear),
arXiv:1209:5585v3, arXiv:1209:5586, K. Ishikawa and Y. Tobita
COMMENT : Seminar

DAY & TIME : 5/24 (Fri.) 10:30-12:00, 13:30-
SPEAKER : T. Goto (KEK)
TITLE : Flavor Physics and Beyond the Standard Model
ABSTRACT : In this seminar, I will review current status of the flavor physics and discuss the impacts of recent experimantal results on the search for new physics beyond the Standard Model. The covered topics will be flavor changing processes in the B meson decays (b-->s transitions, B-B_bar mixings etc.) and the lepton flavor violating processes of muons and tau leptons. As for the new physics model, I mainly focus on the supersymmetric models.
COMMENT : Seminar

DAY & TIME : 5/17 (Fri.) 10:30-12:00, 13:30-
SPEAKER : M. Tanimoto (Nigata Univ.)
TITLE : Probing supersymmetry in B meson decays facing the recent LHC data
ABSTRACT : The LHC experiments are now going on to discover new physics, for which the supersymmetry (SUSY) is one of the most attractive candidates. The SUSY signals have not yet observed. The lower bounds of the superparticle masses increase gradually. On the other hand, the LHCb collaboration has reported new data of the CP violation of $B$ mesons and the branching ratios of rare B decays. There are new sources of the CP violation if the SM is extended to the SUSY models. The soft squark mass matrices contain the CP-violating phases, which contribute to the flavor changing neutral current with the CP violation. Therefore, we expect the effect of the SUSY contribution in the CP-violating phenomena although the clear deviation from the prediction of the SM has not been observed yet in the LHCb experiment. The dominant contribution of the SUSY is the gluino-squark mediated flavor changing process for the $B$ meson decays. By putting the present experimental data, we predict the CP violation of the B meson decays, in which the interesting one is the B_s\to\phi\phi decay.
COMMENT : Seminar

DAY & TIME : 5/10 (Fri.) 10:30-12:00, 13:30-
SPEAKER : M. Ibe (ICRR)
TITLE : Pure Gravity Mediation of Supersymmetry Breaking
ABSTRACT : The recent discovery of the Higgs boson with a mass at around 126GeV point to the sfermion mass scales at around tens to hundreds TeV scale in the minimal supersymmetric Standard Model. I show that such heavy sfermion model allows us a very simple but phenomenologically viable model of the MSSM where all the supersymmetry breaking effects are mediated by purely Planck suppressed operators (i.e. Pure Gravity Mediation). I'm going to discuss theoretical, phenomenological and cosmological aspects of the pure gravity mediation model.
COMMENT : Seminar

DAY & TIME : 4/26 (Fri.) 13:30-18:00
SPEAKER : H. Kawai (Kyoto Univ.)
TITLE : Desert and the Naturalness
ABSTRACT : We evaluate the bare parameters of the standard model. It truns out that the standard model can be valid to the Planck or the string scale, which suggests that the desert is possible. In other words, we might have almost nothing other than the standard model particles below the string scale. Then we discuss a possible mechanism to explain the naturalness in that case. We show that the low energy effective action of quantum gravity or string theory is not a simple local action but a multi-local one, if the theory involves the topology change of the space time. We speculate how the naturalness problem can be solved in such framework.
COMMENT : Afternoon Seminar

DAY & TIME : 4/19 (Fri.) 10:30-12:00
SPEAKER : O. Seto (Hokkai Gakuen Univ.)
TITLE : Dark matter models with large annihilation into photons
ABSTRACT : Last year, by analyzing Fermi-LAT data, a possible hint of dark matter annihilation has been reported. According to that analysis, gamma ray excess with line spectrum at the energy about 130 GeV apparently exist. However, required annihilation cross section to reproduce such a gamma line excess from dark matter annihilation is rather large. Thus, sensible model construction is challenging. I introduce two particle models including dark matter candidate with such a large enough annihilation cross section into two photons. One is a supersymmetric model where dark matter candidate is Dirac sneutrino, the other is an extra U(1) model where its extra gauge boson is dark matter candidate.
E-PRINT : K.-Y.Choi and O.Seto, Phys. Rev. D 86, 043515 (2012) [Erratum-ibid.D 86, 089904 (2012)], K.-Y.Choi, H.M.Lee and O.Seto, arXiv:1304.0966 [hep-ph].
COMMENT : Morning Seminar

DAY & TIME : 4/12 (Fri.) 10:30-12:00
SPEAKER : S. Kanemura (University of Toyama)
TITLE : Higgs as a Probe of New Physics
ABSTRACT : We discuss various aspects of physics of the Higgs sector in light of the recent results at the LHC. The connection between the Higgs boson physics and various new physics models beyond the standard model is emphasised. We then show future prospects for collider physics including the international linear collider project, and discuss how the new physics can be tested at these future colliders.
COMMENT : Morning Seminar

DAY & TIME : 4/12 (Fri.) 13:30-
SPEAKER : S. Kanemura (University of Toyama)
TITLE : Higgs boson dynamics: Weak and Light? or Strong but Light?
ABSTRACT : A Higgs boson was discovered last summer, and its mass was measured to be 125 GeV. We discuss a mechanism to produce this observed value for the mass in the framework of supersymmetric theory. We construct a model where a UV free supersymmetric Yang-Milles theory with a certain flavor produces composite Higgs superfields below the confinement scale. In order to realize the first order phase transition of electroweak gauge symmetry, which is required for successful electroweak baryogenesis, the confinement scale turns out to be around 10 TeV or higher, below which an extended supersymmetric Higgs sector with the mass of the SM like Higgs boson to be 125 GeV is predicted as a low energy effective theory. We also discuss the collider phenomenology of this model at the LHC and the International Linear Collider.
COMMENT : Afternoon Seminar

Back to Home (Japanese) Back-Numbers etc.