Seminar - Particle Physics Theory Group

2010年度のセミナー


date	15 February (Tue) 15:30〜 H711
Name	Daisuke Kadoh (riken)
Title	SUSY on the lattice
Abstract	Recently, a new approach to study non-perturbative effects of supersymmetric theories from lattice theory has been progressing. Especially, some successes have been achieved in low dimensional theories. In this talk, I'll review the present status of lattice supersymmetry and examine a lattice formulation of Wess-Zumino model in 2 and 3 dimensions.

　


date	22 February (Tue) 15:30〜 H711
Name	Minoru Eto (riken)
Title	Chiral Magnetic Effect from Q-balls
Abstract	We apply a generic framework of linear sigma models for revealing a mechanism of the mysterious phenomenon, the chiral magnetic effect, in quark-gluon plasma. An electric current arises along a background magnetic field, which is given rise to by Q-balls (non-topological solitons) of the linear sigma model with axial anomaly. We find additional alternating current due to quark mass terms. The hadronic Q-balls, baby boson stars, may be created in heavy-ion collisions.

　


Info.	We had three seminars on 2/1
date	1 February (Tue) 13:00〜 H711
Name	Yukihiro Mimura (National Taiwan U)
Title	CP violating lepton asymmetry from semi-leptonic B decays as a probe of new physics
Abstract	We investigate the dimuon CP asymmetry from the B decay modes, recently observed at 3.2 sigma　deviation from the Standard Model by the D0 collaboration, in order to probe new physics.　A large amount of flavor violation between the second and the third generation is generated due to the large neutrino atmospheric mixing angle and this flavor violation can be responsible for　the large CP asymmetry in grand unified theories. We exhibit the GUT scenarios and the constraints from the other flavor violating processes. We also study the modification of the absorptive part of the mixing amplitude.

date	1 February (Tue) 14:30〜 H711
Name	Koji Tsumura (National Taiwan U)
Title	Phenomenology in the Higgs Triplet Model with the A_4 Symmetry
Abstract	We discuss the phenomenology of doubly and singly charged Higgs bosons (of SU(2)_L-triplet fields) in the simplest A_4-symmetric version of the Higgs Triplet Model. Mass eigenstates of these Higgs bosons are obtained explicitly from the Higgs potential. It is shown that their decays into a pair of leptons have unique flavor structures which can be tested at the LHC if some of their masses are below the TeV scale. Sizable decay rates for tau to bar(mu) e e and tau to bar(e) mu mu can be obtained naturally while other tau to l l' l'', mu to bar(e) e e, and l to l' gamma are almost forbidden in this model. Contributions of these Higgs bosons to the non-standard interactions of neutrinos are also considered.

date	1 February (Tue) 16:00〜 H711
Name	Keiko I. Nagao (National Tsing Hua University)
Title	Dark Matter in Inert Triplet Higgs Model
Abstract	Since the standard model (SM) does not accommodate dark matter candidate, new physics models are expected. In the inert triplet model (ITM), we introduce one triplet scalar which does not couple to the SM fermions. In this talk I plan to talk about the signature of the DM candidates in the model.

　


date	18 January (Tue) 15:30〜 H711
Name	Motohiko Yoshimura (Okayama U)
Title	Solitons and alike objects for precision neutrino　mass spectroscopy
Abstract	TBA

　


date	5 January (Thu) 15:30〜 H711
Name	Yuji Tachikawa (IPMU&IAS)
Title	On S-duality of 5d super Yang-Mills on S1
Abstract	It is well-known that the 4d N=4 super Yang-Mills (SYM) has an S-duality exchanging W-bosons and monopoles. We discuss how it can be extended to the full spectrum of Kaluza-Klein W-bosons when the 4d N=4 theory is realized as the compactification of 5d super Yang-Mills on S1. This talk is based loosely on 1009.0339 and on an unpublished work.

　


date	14 December (Tue) 15:30〜 H711
Name	Kin-ya Oda (Osaka U)
Title	Unitarity in Dirichlet Higgs Model
Abstract	We show that a five dimensional Universal Extra Dimension model, compactified on a line segment, is consistently formulated even when the gauge symmetry is broken solely by non-zero Dirichlet boundary conditions on a bulk Higgs field, without any quartic interaction. We find that the longitudinal W+W- elastic scattering amplitude, under the absence of the Higgs zero-mode, is unitarized by exchange of infinite towers of KK Higgs bosons. Resultant amplitude scales linearly with the scattering energy, exhibiting five dimensional nature. A tree-level partial-wave unitarity condition is satisfied up to 6.7 (5.7) TeV for the KK scale 430 (500) GeV, favored by the electroweak data within 90% CL.

　


date	7 December (Tue) 15:30〜 H711
Name	Masaki Jung Soo Yang (Tokyo University)
Title	Charged Lepton Flavor Violation in the Supersymmetric Models
Abstract	Supersymmetry(SUSY) is a candidate of beyond the standard model. However, there are still unsolved problem, the origin of SUSY breaking, or too many soft breaking parameters, and so on. Especially, these SUSY breaking parameters generally depend on fermion generations, sizable flavor violation processes are induced and conflict with experimental bounds. It is called "SUSY flavor problem". To solve these problems, many SUSY breaking model building and phenomenological research are proceeding. Nevertheless, other flavor violation sources are brought by higher scale structure, such as GUT or seesaw mechanism. Observation of charged lepton flavor violation (cLFV) is one of clear probe to verify these models. This talk is composed of some review of cLFVs in the SUSY models, and recent study of cLFVs. In the MSSM, cLFV is induced by two effects, gaugino and Higgs contribution. We analyse these effects and discuss competetion of two effects in the main parameter regions.

　


date	30 November (Tue) 16:00〜 H711
Name	Takahiro Tanaka (YITP)
Title	Requirement on the initial conditions to maintain gauge invariance during inflation
Abstract	It has been an issue of debate whether the inflationary infrared(IR) divergences are physical or not. Our current claim is that, at least, in single-field models, the answer is "No," and that the spurious IR divergence is originating from the careless treatment of the gauge modes. We explicitly show that the IR divergence is absent in the genuine gauge-invariant quantity to the second order in the slow-roll approximation, also including the contributions from the gravitational wave perturbations. The key issue is to assure the gauge invariance in the choice of the initial vacuum, which is a new concept that has not been considered in the conventional calculation of cosmological perturbations.

　


date	16 November (Tue) 15:30〜 H711
Name	Sang-Woo Kim (Osaka University)
Title	Supersymmetry non-renormalization theorem from a computer and the AdS/CFT correspondence.
Abstract	We perform Monte Carlo simulation of the plane-wave matrix model or the BMN matrix model, which has 16 supercharges. The model has many degenerate supersymmetric vacua, and by picking up a particular one, we can obtain 4d N=4 super Yang-Mills theory on RxS^3 in the planar limit based on the idea of a novel large-N reduction. We study correlation functions of non-extremal operators, and find clear evidence that the supersymmetry non-renormalization theorem is at work for three-point functions. For four-point functions, we observe small violation of the non-renormalization property, which is consistent with a result obtained from the AdS/CFT correspondence.

　


date	9 November (Tue) 15:30〜 H711
Name	Katsushi Ito (TITECH)
Title	TBA equations for Minimal surfaces in AdS
Abstract	We study classical open string solutions with a null polygonal boundary in AdS_3 in relation to gluon scattering amplitudes in N=4 super Yang-Mills at strong coupling. We derive the set of integral equations and identify them with the thermodynamic Bethe ansatz (TBA) equations of the homogeneous sine-Gordon models. We also study six-point gluon scattering amplitudes by investigating the TBA equations of the Z_4-symmetric integrable model and using conformal field theory perturbation.

　


date	2 November (Tue) 15:30〜 H711
Name	Haruhiko Terao (Nara women's University)
Title	On the SU(N) gauge beta functions in the conformal window
Abstract	It has been known that QCD becomes scale invariant when the number of flavors is set in the so-called conformal window. At the lower edge of the window, the fixed point appears in the strongly coupled region and, therefore, the dynamics there is unclear. We discuss qualitative behavior of the SU(N) gauge beta function around the conformal window by means of the non-perturbative renormalization group. It will be shown that the beta function possesses not only an IR but also a UV fixed point in the conformal window and transforms continuously to those out of the window through pair annihilation of these fixed points.

　


date	12 October (Tue) 15:30〜 H711
Name	Hidenori Fukaya (Osaka University)
Title	Chiral perturbation theory in finite volume
Abstract	In a finite volume, contrary to its name, Chiral perturbation theory (ChPT) requires a "non-perturbative" treatment to control the vacuum fluctuation in the quark mass zero limit. In the so-called epsilon expansion, we separately treat the vacuum mode of pions and perform group integrals nonperturbatively. This epsilon expansion is, however, valid only when the pion mass Mpi is much smaller than the volume size inverse 1/L: Mpi L << 1. We develop a new expansion of ChPT which remains valid even beyond Mpi L = O(1) and smoothly interpolates to the conventional p (large volume) expansion. Our results are useful in precisely estimating the finite volume effects in lattice QCD simulations.

　


date	5 October (Tue) 15:30〜 H711
Name	Tomohisa Takimi (国立台湾大学)
Title	Nambu-Poisson bracket and Non-commutative geometry
Abstract	Recently, we studied the M-theory models with the structure of Nambu-Poisson bracket, which is the extension of the Poisson bracket. Then such models are expected to have analogous structure to the non-commutative geometry. Then it can be an M-theory origin of the non-commutative gauge theory on the D-branes. I would like to talk about our recent studies of the Nambu-Poisson bracket and its relations to the non-commutative geometry.

　


date	13 July (Tue) 15:30〜 H711
Name	Wade Naylor (Osaka University)
Title	Towards detection of motion-induced radiation?
Abstract	We discuss the results of theoretical simulations of a proposed experiment using pulsed laser irradiation of a semi-conductor diaphragm (SCD) in a superconducting microwave cavity. Because the detection apparatus uses a single photon detection Rydberg beam method the analysis can be simplified to study the number of photons emitted in a given cavity mode.

　


date	6 July (Tue) 15:30〜 H711
Name	Kenji Kadota (University of Michigan)
Title	The effects of SUSY seesaw on the dark matter and LHC signals
Abstract	The effects of the GUT scale seesaw mechanisms on the dark matter and LHC signals will be discussed. For the collider signals, the enhancement of the tau lepton signals at LHC in the constrained seesaw scenario will be presented. For the dark matter, the complete disappearance of the focus point regions and the appearance of the sneutrino coannihilation regions, in consistence with the thermal neutralino relic abundance, will be discussed.

　

date	29 June (Tue) 15:30〜 H711
Name	Tadashi Takayanagi (IPMU, Univ. of Tokyo)
Title	Mini Black Holes and Quantum Quench from AdS/CFT
Abstract	AdSブラックホールと有限温度CFTがホログラフィーで等価であることは良く知られており、例えば最近盛んに研究されているAdS/CFTの物性物理への応用においても非常に重要な役割を担っている。しかしながら、このような熱平衡状態における対応を、より一般の非平衡系へ拡張する方法に関しては、まだ良く分かっていないことが多い。例えば、系を二つに分けて、片方だけ加熱するような非平衡状態は、AdS/CFTを用いてどのように記述することができるだろうか？このような系では二つの異なる温度を持つことが可能であるが、ブラックホールの温度は通常一つしかない。本セミナーでは、そのような状態を、D-braneをAdS/CFTの中に導入することによって記述できることを説明したい。回転しているD-braneを考えるとD-brane上にあたかもブラックホールがあるような状態「ミニ・ブラックホール」が実現されるのである。また最後に、その応用例として、物性物理などで最近話題となっている「量子クエンチ」をAdS/CFTを用いて記述する方法を説明したい。

　


date	24 June (Thur) ！16:30〜 H711
Name	Takehiko Asaka (Niigata Univ.)
Title	Neutrino Masses and Baryon Asymmetry of the Universe
Abstract	振動実験が指摘したニュートリノ質量を説明する新しい素粒子模型に基づいて宇宙バリオン数の起源を考察する。本公演では、質量が田弱スケール以下の右巻きニュートリノを導入した模型でのバリオン数生成機構について解説する。特に、バリオン数生成量とアクティブニュートリノの質量・混合・ＣＰ位相の間の関係について考察する。

　


date	15 June (Tue) 15:30〜 H711
Name	Kenji Nishiwaki (Kobe Univ.)
Title	Some remarkable topics associated with two extra dimensions
Abstract	現象論的な余剰次元の研究は余剰次元が1つの場合でなされる場合が多いですが、余剰次元が2つに増えると、余剰次元の幾何学的な自由度が増えたことによる興味深い物理が新たに現れることがあります。本講演では、本質的に余剰次元の幾何学に由来するCPの破れの機構をまずご紹介します。このCPの破れの起源は余剰次元が複素構造を持つことで、$T^2/Z_4$という単純なオービフォールドで実現することが可能です。この機構はスカラー場を導入する必要がないので、ゲージ・ヒッグス統一模型への応用が期待されます。又、6次元Universal Extra Dimension模型のヒッグス粒子のLHCでの(ループ過程を通した)生成・消滅反応にも簡単に触れたいと思います。こちらも余剰次元の幾何学構造に由来するKK粒子スペクトラムの形が本質的な役割を果たします。

　


date	8 June (Tue) 15:30〜 H711
Name	Fumihiro Takayama (YITP, Kyoto Univ.)
Title	SuperWIMP (超微弱相互作用粒子に関連した話題について)
Abstract	素粒子標準模型は今までのところさまざまな実験結果をよく説明してきている一方で、ニュートリノの質量の発見や　暗黒物質のさまざまな状況証拠は標準模型へ新粒子の付加を示唆している。私は暗黒物質の候補として超対称標準模型や余剰次元模型のなかに現れるグラビティーノの様な超微弱相互作用粒子とそれに関係した長寿命粒子に注目して　その初期宇宙での役割、現在の宇宙線の起源としての可能性、そして衝突型実験での探索について　よく知られた暗黒物質の候補WIMP（弱い相互作用をする重い粒子）の場合と比較しながら議論する。

　


date	4 June (Fri) 10:30〜 H711
Name	Mohab Abou Zeid
Title	Noncommutative gravity with torsion and vortex solitons
Abstract	A Lorentzian theory of noncommutative gravity with torsion coupled to U(1) Chern-Simons gauge fields and charged matter is investigated. The construction is a generalisation of the well-known relationship between three-dimensional gravity and Chern-Simons theory and it can be viewed as a toy model for a noncommutative deformation of the U(2) × U(2) Aharony-Bergman-Jafferis-Maldacena model. Utilising the Harvey-Kraus-Larsen solution-generating technique, BPS solutions of the field equations are constructed which are exact for all values of the noncommutativity parameter θ, regular for θ≠0 and singular in the limit θ → 0. The gravitational interpretation of the solutions is discussed.

　


date	25 May (Tue) 15:30〜 H711
Name	Takuya Kanazawa (Univ. of Tokyo)
Title	Exact results for two-color QCD at low and high density
Abstract	We consider the chiral extension of the real Ginibre emsemble of random matrices with dynamical flavors to study the spectrum of the Dirac operator in two-color QCD with nonzero baryon chemical potential. We show that at maximum non-Hermiticity the random-matrix model is equivalent to the low-energy effective theory at high density in the epsilon regime. We obtain the microscopic spectral density of the Dirac eigenvalues in the limits of both strong and weak non-Hermiticity for a general number of flavors. We illustrate the main characteristics of the spectrum and comment on the sign problem for non-degenerate quark masses. Our results can in principle be checked by lattice QCD simulations.

　


date	11 May (Tue) 15:30〜 H711
Name	日笠健一氏 (東北大学)
Title	Helicity amplitudes and new physics
Abstract	100 GeV を超えるエネルギーの物理では，弱い相互作用によるパリティの破れのため，粒子の偏極による違いが本質的である。ヘリシティ振幅はこのような場合に有用な形式である。特に，球ベクトルと回転行列を用いて定式化すると，さまざまな角分布などのふるまいを容易に理解することができる。標準模型を超える超対称性や余剰次元などの物理では高いスピンの粒子が現れるが，その効果をヘリシティ振幅を用いて調べる。

　


date	11 May (Tue) 15:30〜 H711
Name	岩崎　皓氏(京都大学　(東京工業大学よりの受託学生))
Title	曲がった時空上での行列模型と場の理論の関係における最近の進展
Abstract	IIB行列模型は超弦理論を非摂動的に定式化するモデルの中の有力な候補であると考えられている。2006年に花田・川合・木村によってこの行列模型に対する新たな解釈が与えられた。これによると行列は曲がった時空上で定義された共変微分として解釈される。この観点に立つと一般座標変換や局所Lorentz対称性等、時空が持つべき対称性が自然に行列模型に含まれていることを見て取ることが可能である。またこの解釈に基づいた時に得られる行列の運動方程式が真空中のEinstein方程式であることはIIB行列模型が曲がった時空を古典解として内包することを示唆している。しかしながら実際このような古典解としての曲がった時空の周りでの行列模型の量子論を展開した際、これがどのような理論となるかについては詳細に確かめられてこなかった(平坦時空の場合については同じく平坦時空上の場の理論と1対1対応することが知られている)。今回我々は具体的に特定の時空周りでの行列模型の揺らぎを計算し、これが平坦時空の場合と同じく場の理論と対応するものなのかどうかを考察した。考える背景時空によって場の理論との対応関係は異なり、中には行列模型に変更を施さないと望ましい場の理論との対応関係が得られない場合もある。今回のセミナーではそうした個々の状況についての現在までの理解と今後議論を拡張する上での困難等について話したい。

　


date	27 April (Tue) 15:30〜 H711
Name	伊藤　悦子氏(大阪大学)
Title	Search for the IR fixed point using lattice simulations
Abstract

　


date	21 April (Wed) 15:30〜 H601
Name	Prof. Ernest Ma (U.C. Riverside)
Title	New Dark Left-Right Model: CDMS, LHC, and Lepton Flavor Violation

　


date	13 April (Tue) 15:30〜 H711
Name	大木　洋氏(大阪大学)
Title	Flavor structure from the higher dimensional super Yang-Mills theory

過去のセミナー