2009年度のセミナー

date 10 Mar (Tue) 13:30〜 H711
Name Prof. Paul Frampton (University of North Carolina)
Title Primordial Black Holes as All Dark Matter
Refs arXiv:1001.2308v1 [hep-ph]
date 9 Mar (Tue) 15:30〜 H711
Name Dr. Seong Chan Park (IPMU)
Title Kaluza-Klein Dark matter
AbstractI would review Kaluza-Klein dark matter and its phenomenology. In particular, I would consider the effect of mass of bulk fermions in light of the recent Pamela, ATIC and Fermi anomalies. A possibility of obtaining natural Yukawa hierarchy will be also discussed.
date 23 Feb (Tue) 15:30〜 H711
Name 福間 将文氏（京大）
Title Universal description of viscoelasticity
Abstract粘弾性体の普遍的な記述法について解説する。具体的には、塑性変形を記述する力学変数を新たに導入し、粘弾性体の運動を世界体積上の場の理論として取り扱う。その際、理論に「foliation preserving diffeomorphism」の対称性が自然に導入されるが、この対称性は、弾性体と粘性流体の二つの極限を自然につなぐと同時に、有効理論が取りうる形をほぼ一意的に決めてしまう。時間が許せば、いくつかの応用についても解説する予定である。
Refs arXiv:0907.0656
date 26 Jan (Tue) 15:30〜 H711
Name 村山斉氏（ＩＰＭＵ）
Title キャンセル
date 21 Jan (Thu) 15:30〜 H711
Name Prof. SUMIT R. DAS (Kentucky)
Title SPINS AND EMERGENT GAUGE FIELDS AT LIFSHITZ POINTS
date 19 Jan (Tue) 15:30〜 H711
Name 黒木経秀氏（立教大学）
Title Spontaneous supersymmetry breaking in large-$N$ matrix models with slowly varying potential
AbstractWe construct a class of matrix models, where supersymmetry (SUSY) is spontaneously broken at the matrix size $N$ infinite. The models are obtained by dimensional reduction of matrix-valued SUSY quantum mechanics. The potential of the models is slowly varying, and the large-$N$ limit is taken with the slowly varying limit. First, we explain our formalism, introducing an external field to detect spontaneous SUSY breaking, analogously to ordinary (bosonic) symmetry breaking. It is observed that SUSY is possibly broken even in systems in less than one-dimension, for example, discretized quantum mechanics with a finite number of discretized time steps. Then, we consider spontaneous SUSY breaking in the SUSY matrix models with slowly varying potential, where the external field is turned off after the large-$N$ and slowly varying limit, analogously to the thermodynamic limit in statistical systems. On the other hand, without taking the slowly varying limit, in the SUSY matrix model with a double-well potential whose SUSY is broken due to instantons for finite $N$, a number of supersymmetric behavior is explicitly seen at large $N$. It convinces us that the instanton effect disappears and the SUSY gets restored in the large-$N$ limit.
date 12 Jan (Tue) 15:30〜 H711
Name 川村嘉春氏（信州大学）
Title 2次元オービフォールド上のSU(N)ゲージ理論の境界条件の分類について
Abstractオービフォールド上の場の理論の様々な利点を紹介した後、2次元オービフォールドを含む6次元時空上のゲージ理論における境界条件の同値類などについて議論する。具体的には、2次元オービフォールドとして、主にT^2/Z_3を用いて、SU(N)ゲージ理論における境界条件、ゲージ変換性と同値類、細谷機構などゲージ対称性に関する特徴について報告する。
Refs Y. Kawamura, T. Kinami and T. Miura, PTP 120 (2008), 815; Y. Kawamura and T. Miura, PTP 122 (2009), 847.
date 22 Dec (Tue) 15:30〜 H711
Name 甲田昌也（埼玉大）
Title The strongly coupled fourth family and a first-order electroweak phase transition
AbstractWe discuss a finite-temperature electroweak phase transition in models of dynamical electroweak symmetry breaking due to strongly coupled fourth-family fermions. In this kind of models, multiple Higgs bosons appear as the bound states of the fourth-family fermions and their loop effects may induce a strongly first-order electroweak phase transition, which is required for the electroweak baryogenesis. We examine whether this possibility of the strongly first-order phase transition can be realized based on the low-energy effective theory, which consists of the fourth-family quarks and two SU(2)-doublet composite Higgs fields. Through the analysis of the finite-temperature effective potential, we show that the strongly first-order phase transition is possible even if the mass of the lightest neutral scalar Higgs is larger than the LEP lower bound, as long as the masses of the fourth-family quarks are smaller than about 300 GeV.
date 15 Dec (Tue) 16:20〜 H711
Name 松本重貴氏（富山大）
Title Can WIMP dark matter overcome the Nightmare scenario?
Abstract標準模型を超える新しい物理は通常O(1)TeVスケールにあると期待されている. しかしながら, 新しい物理がO(10)TeVにある場合でも, ヒッグス質量への輻射補正の問題において, たかだか1%の微調整が必要なだけである. この様なケースでは, 近い将来の実験で新しい物理のシグナルを見つけることは困難であり、しばしばナイトメアシナリオと呼ばれる. 一方暗黒物質がWIMPであるならば, その質量は10GeV-1TeVと見積もられる. このため, 新しい物理のシグナルとして, すくなくとも暗黒物質シグナルだけは近い将来に観測される可能性がある. 今回, ナイトメアシナリオにおいてWIMP暗黒物質が本当に近い将来の観測及び実験で測定可能であるかどうか、直接検出、宇宙観測、LHC及びILCにおける加速器実験を考え定量的に評価する.
date 8 Dec (Tue) 15:30〜 H711
Name 三角樹弘氏（京大基研）
Title Finite-temperature spectral functions of the mesons in AdS/QCD
AbstractWe use the soft-wall AdS/QCD model to investigate the finite-temperature effects on the spectral functions of the mesons. The dissociation of the meson tower onto the AdS black hole leads to the in-medium mass shift and the width broadening in a way similar to the lattice QCD results for the heavy quarkonium at finite temperature. We also show the momentum dependence of the spectral function and find it consistent with screening in a hot wind.
date 1 Dec (Tue) 15:30〜 H711
Name 八田 佳孝 氏（筑波大）
Title Polarized DIS in N=4 SYM: Where is spin at strong coupling?
AbstractUsing the AdS/CFT correspondence, we calculate the polarized structure functions in strongly coupled N=4 supersymmetric Yang-Mills theory deformed in the infrared. We find that the flavor singlet contribution to the g_1 structure function is vanishingly small, while the flavor non-singlet contribution shows the Regge behavior at small-x with an intercept slightly less than 1. We explicitly check that the latter satisfies the moment sum rule. We discuss the `spin crisis' problem and suggest that at strong coupling the spin of a hadron entirely comes from the orbital angular momentum.
Refs arXiv:0905.2493
date 24 Nov (Tue) 15:30〜 H711
Name 丸吉一暢氏（京大基研）
Title New Seiberg Dualities from N=2 Dualities
Abstracte propose a number of new Seiberg dualities of N=1 quiver gauge theories. The new Seiberg dualities originate in new S-dualities of N=2 superconformal field theories recently proposed by Gaiotto. N=2 S-dual theories deformed by suitable mass terms flow to our N=1 Seiberg dual theories. We show that the number of exactly marginal operators is universal for these Seiberg dual theories and the 't Hooft anomaly matching holds for these theories. These provide strong evidence for the new Seiberg dualities. Furthermore, we study in detail the Klebanov-Witten type theory and its dual as a concrete example. We show that chiral operators and their non-linear relations match between these theories. These arguments also give non-trivial consistency checks for our proposal.
date 17 Nov (Tue) 15:30〜 H711
Name 佐々木節氏（京大基研）
Title Non-Gaussianity from Inflation
date 12 Nov (Thu) 16:30〜 H711
Name 相阪 有理 氏（Sao Paulo State univ.）
Title Some Recent Developments in Pure Spinor Formalism
AbstractPure spinor formalism is a new worldsheet formalism for quantizing the superstring in a super Poincare covariant manner. The formalism provides a powerful way to compute scattering amplitudes. and is very promising for describing superstrings in general Ramond-Ramond backgrounds. In this talk, we try to give an overview of the formalism with some emphasis on my own works.
date 10 Nov (Tue) 15:30〜 H711
Name 八木絢彌氏（ラトガース大学）
Title Chiral Algebras of (0,2) Models: Beyond Perturbation Theory
AbstractThe chiral algebras of two-dimensional sigma models with (0,2) supersymmetry are infinite-dimensional generalizations of the chiral rings of (2,2) models. Perturbatively, they enjoy rich mathematical structures described by sheaves of chiral differential operators. Nonperturbatively, however, they vanish completely for certain (0,2) models with no left-moving fermions. In this talk, I will explain how this vanishing phenomenon takes places. The vanishing of the chiral algebra of a (0, 2) model implies that supersymmetry is spontaneously broken in the model, which in turn suggests that no harmonic spinors exist on the loop space of the target space. In particular, the elliptic genus of the model vanishes, thereby providing a physics proof of a special case of the H醇rhn-Stolz conjecture.
date 4 Nov (Wed) 15:30〜 H711
Name 大河内 豊 氏（Perimeter Institute for Theoretical Physics）
Title On Confinement Index
AbstractWilson-'t Hooft loopは、ゲージ理論の相構造の分類において強力なツールであることが知られている。超対称性を保つ真空では、その振る舞いを定量的に議論する事が可能である。セミナーでは、４D N=1 pure YM理論の超対称性を保つ真空での、ウィルソントフーフトループの振る舞いを明らかにし、さらに、さまざまなヒッグス場を含んだ、多くのクラスの理論におけるウィルソントフーフトループの振る舞いを決定する。
Refs K. Konishi and Y. Ookouchi, 0909.3781 [hep-th]
date 9 Oct (Fri) 13:00〜 H711
Name 安達 裕樹 氏（神戸大）
Title CP violation in 5D gauge-Higgs unification
AbstractWe study the neutron electric dipole moment (EDM) in a five-dimensional SU(3) gauge-Higgs unification compactified on M4 x S1/Z_2 space-time including a massive fermion. We point out that to realize the CP violation is a nontrivial task in the gauge-Higgs unification scenario and argue how the CP symmetry is broken spontaneously by the vacuum expectation value of the Higgs, the extra space component of the gauge field. We emphasize the importance of the interplay between the vacuum expectation value of the Higgs and the Z2 -odd bulk mass term to get physically the CP violation. We then calculate the one-loop contributions to the neutron EDM as the typical example of the CP violating observable and find that the EDM appears already at the one-loop level, without invoking the three-generation scheme. We then derive a lower bound for the compactification scale,w hich is around 2.6 TeV, by comparing the contribution due to the nonzero Kaluza-Klein modes with the experimental data.
date 15 Sep (Tue) 15:30〜 H711
Name 深谷 英則 氏（名古屋大）
Title Dirac operator spectrum and chiral symmetry breaking
AbstractWe study the distribution of Dirac operator eigenvalues within chiral perturbation theory. Our new NLO calculation with arbitrary number of flavors shows a logarithmic curve in the bulk region (p-regime) smoothly connecting to the microscopic region(epsilon-regime) which is expressed by the modified Bessel functions. This result opens a new possibility for lattice QCD of extracting not only the chiral condensate but also the other low-energy constants from the Dirac operator spectrum.
Refs P.H.Damgaard and H. Fukaya, JHEP01(2009)052 [arXiv:0812.2797]
date 28 July (Tue) 15:00〜 H711
Name 山津 直樹 氏(九大)
Title 素粒子の世代構造とノンコンパクトなホリゾンタル対称性
Abstract標準理論を越える自然法則を探求する方法としてカイラルな三世代のクォークやレプトンの存在とその質量階層性に注目し，その記述として四次元の有効場の理論においてホリゾンタル対称性を持つ模型を考えることができるだろうという観点から研究を行っています．そのような観点を満たすであろう模型である，ノンコンパクト群のホリゾンタル対称性と超対称性を持つベクターライクな模型に基づいて議論しています．この模型の特徴は『自発的世代の生成機構』と呼ばれるクォークやレプトンのカイラルな世代の自発的な生成の機構と，その機構から現れる湯川相互作用が階層的な構造を持つことなので,今回の話は主にこれらの特徴に関して説明を行いたいと思います．
date 23 July (Thu) 15:00〜 H711
Name 桜井 一樹 氏(KEK)
Title LHC signature of SUSY models with non-universal sfermion masses
AbstractLHC signature of E6 GUT models with non-Abelian horizontal symmetry is investigated. We perform the Monte Carlo simulation and demonstrate to find several characteristic signatures of this model in the early stage of the LHC. We discuss a method to discriminate this model from CMSSM. The mass measurement of superparticles is also studied.
date 21 July (Tue) 15:00〜 H711
Name 高橋　亮 氏(基研)
Title Cascade Hierarchy and Grand Unified Theory
Abstractカスケード型と呼ばれる階層構造をもつ質量行列がニュートリノのディラック質量行列を表す場合、シーソー機構の枠組みで実験で測られるMNS行列を精度良く説明できることが知られている。今回は、そのカスケード的な階層構造をクォークセクターへも適用し、クォーク・レプトンの質量の階層性、世代混合を統一的な描像で理解することを試みる。また、カスケード的な階層構造の大統一理論への埋め込みについても議論する。
date 14 July (Tue) 16:30〜 H711
Name 岡田 宣親 氏(KEK)
Title $\nu$-Gauge Mediated Supersymmetry Breaking and Phenomenology
AbstractWe show that when the supersymmetric SU(5) model is extended to explain small neutrino masses by the type III seesaw mechanism, the new 24-dimensional fields needed for the purpose can act as messengers for transmitting SUSY breaking from a hidden sector to the visible sector. For the three 24 case, the constraints of grand unification and suppressed lepton flavor violation restrict the seesaw scale in this case to be in the narrow range of 10^{12}-10^{13} GeV. The model predicts (i) a stable LSP gravitino with mass in the range of 1-10 MeV which can be a cold dark matter of the universe; (ii) a stau NLSP which is detectable at LHC; (iii) a lower bound on the branching ratio $BR(\mu \to e \gamma)$ larger than $10^{-14}$ testable by the ongoing MEG experiment as well as characteristic particle spectrum different from other SUSY breaking scenarios.
Refs R.N. Mohapatra, N. Okada and H.B. Yu, ``$\nu$-GMSB with Type III Seesaw and Phenomenology,'' Phys. Rev. D78, 075011 (2008) [arXiv:0807.4524 [hep-ph]] and work in progress
date 7 July (Tue) 15:00〜 H711
Name 向山 信治 氏(IPMU)
Title Aspects of Horava-Lifshitz cosmology
AbstractIn the first half of this talk I will review the basic idea of the power-counting renormalizable theory of gravitation recently proposed by Horava. In the second half I will talk about some cosmological implications of the theory. In particular, I will show that the anisotropic scaling with a dynamical critical exponent z=3 leads to scale-invariant cosmological perturbations in non-inflationary epoch and that the absence of local Hamiltonian constraint leads to a component similar to cold dark matter as integration "constant".
date 30 June (Tue) 15:00〜 H711
Name 長尾 浩明 氏(新潟大)
Title コヒーレント振動からの粒子生成
Abstractインフレーションとよばれる宇宙の指数関数的膨張が初期宇宙で起こったことは、宇宙背景輻射の精密測定から確実視されています。我々はインフレーション後の再加熱過程について考察しました。本研究ではコヒーレント振動したスカラー場とフェルミオン、ボゾンとが弱く結合した系を、宇宙膨張を無視した場合について取り扱いました。結果、生成の初期についてはBogoliubov変換の方法を用いて評価することで、コヒーレント振動する場を非相対論的粒子の集団として扱う近似が妥当であると判明しました。また、生成の後期では、フェルミオンとボソンの統計的性質が無視できなり、上記の近似が妥当でないことを数値計算によって示し、その挙動が平均法を用いることで再現出来るということを示しました
date 23 June (Tue) 15:00〜 H711
Name 隅野 行成 氏(東北大)
Title Family Gauge Symmetry as an Origin of Koide's Mass Formula and Charged Lepton Spectrum
AbstractKoide's mass formula is an empirical relation among the charged lepton masses which holds with a striking precision. Recently we have proposed mechanisms to explain origins of the charged lepton spectrum as well as Koide's mass formula, on the basis of $U(3)\times O(3)$ family gauge symmetry. In this talk, I review the basic ideas of these mechanisms.
We adopt a known scenario, in which the charged lepton spectrum is determined by the vacuum expectation value of a scalar field that takes values on 3-by-3 matrix. Within this scenario, we propose a mechanism, in which the radiative correction induced by $U(3)$ family gauge interaction cancels the QED radiative correction to Koide's mass formula. We consider $SU(9)\times U(1)$ symmetry broken down to $U(3)\times O(3)$ symmetry. This leads to a model which predicts Koide's mass formula and the charged lepton spectrum consistent with the experimental values, by largely avoiding fine tuning of parameters. These are discussed within an effective theory. Radiative corrections as well as other corrections to Koide's mass formula have been taken into account.
date 18 June (Thu) 15:00〜 H711
Name 橋本 幸士 氏(理研)
Title Nuclear Force from String Theory
Abstract
date 9 June (Tue) 15:00〜 H711
Name 大野木 哲也 氏(阪大)
Title Determination of the y-parameter from lattice QCD　- strange quark in nucleon as a probe for new physics -
Abstract「核子内のクォーク凝縮」は、核子のカイラル有効理論の基本パラメータで、パイN散乱実験データによる解析などを通じて長く研究されてきた。しかし、ストレンジクォークの寄与はどれくらいあるのかは最近までよく分かっていなかった。一方、このパラメータはレプトンフレーバ─の破れの測定や暗黒物質の探索において核子をターゲットとする実験が提案されており、New Physicsのモデルの精密な予言に欠かせないものとして核子内のストレンジクォーク凝縮再び注目を浴びている。我々の行なっている厳密なカイラル対称性を持つ格子QCD計算にもとづく核子内のストレンジクォーク凝縮パラメータの決定の研究を紹介する。また、その現象論的インパクトについても述べる。
date 21 April. (Tue) 15:30〜 H711
Name 清水 明 氏(東大駒場)
Title Modern theory of quantum measurement and its applications
Abstract Since quantum systems exhibit probabilistic natures, one has to perform many runs of measurements in an experiment. In ordinary experiments, one resets the system before each run in order to prepare the same quantum state |psi> for all runs. Or, alternatively, one prepares many equivalent systems in the same state |psi>, and performs the same measurement independently for each system. In either case, one does not need to know the post-measurement state |psi'> (i.e., the state after the measurement) in order to predict or analyze the results of the experiment.However, one can perform another measurement (of either the same observable or a different observable) on |psi'> before he resets the system. That is, one can perform two subsequent measurements in each run, one for the pre-measurement state |psi> and the other for the post-measurement state |psi'>.In order to preedict or analyze the results of such subsequent measurements, one needs to know |psi'>. To calculate it, one must use something like the so-called projection postulate. By many studies in the last several decades, it has been revealed both theoretically and experimentally that a naive application of the projection postulate gives wrong results that do not agree with experiments on subsequent measurements. To resolve this discrepancy, the quantum measurement theory has been developed. The power of the quantum measurement theory has been demonstrated by many experiments (mostly on quantum optics). In this talk, I will review basic things of the quantum measurement theory. I will also present briefly some applications, such as Quantum Nondemolitoin Measurement, Fundamental Limits of quantum intereference devices, Symmetry breaking when the order parameter does not commute with Hamiltonian.
date 14 April. (Tue) 15:30〜 H711
Name 畦柳 竜生 氏(京大理)
Title Worldsheet analysis of gauge/gravity dualities
Abstract2007年に川合-須山により、D3ブレーンの場合のゲージ/重力対応を弦の世界面の立場から直接的に理解する方法が提案された。本セミナーではこの方法を説明すると共に、低次元Dブレーンの場合への拡張を紹介する。そして、特にWilson loopおよびエントロピーの対応が弦の世界面の立場からどのように理解できるかを議論する(花田政範氏、川合光氏、および松尾善典氏との共同研究に基づく)。
date 6 April. (Mon) 15:30〜 H711
Name 新田 宗人 氏(慶応日吉)
Title Non-Abelian Vortices - Five Years Since the Discovery -
Abstract Five years ago, non-Abelian vortices were discovered in supersymmetric gauge theories and string theory independently. Those were suggested to be a key to understand confinement and duality of supersymmetric QCD, as a generalization of the old idea of Nambu and Mandelstam. In 2005 similar but a bit different non-Abelian vortices happened to be found in the color-flavor locked phase (color superconductor) of dense QCD, which is expected to be realized in core of neutron stars. It has turned out that the moduli space of the vortex solutions in the BPS case has very ample structures, like the one of Yang-Mills instantons. There has been a lot of developments in various directions. For instance, those vortices are candidates of non-Abelian cosmic strings; When two of them collide, their reconnection is inevitable. Vortices in SO and USp generalization has been found recently, and these may offer a fundamental tool toward a proof of the GNO duality. I will explain those developments in these five years.

過去のセミナー