慶應素粒子論セミナー
Keio High Energy Physics Seminars

開催場所: 慶應義塾大学日吉キャンパス第2校舎221番教室 (Keio University Hiyoshi Campus, Second Building, 221)

(2017)


Date:July 3, 2017 15:00pm
Speaker:Takafumi Okubo (Titech)
Title:Quantum periods and prepotential in N = 2 SU(2) SQCD
Abstract:The Seiberg-Witten solution of the N = 2 supersymmetric gauge theory enables us to understand both weak and strong coupling physics of the theory. When we quantize the Seiberg-Witten curve, the solution describes the theory in the Nekrasov-Shatashvili (NS) limit of the Ω background. We study N = 2 supersymmetric QCD with massive hypermultiplets in the NS limit. The prepotential of the low-energy effective theory is determined by the WKB solution of the quantum Seiberg-Witten curve. We calculate the deformed Seiberg-Witten periods around the massless monoplole point explicitly up to the fourth order in the deformation parameter.


Date:June 29, 2017 16:30pm @ Room 222
Speaker:Hironori Mori (YITP)
Title:Physical and Mathematical Applications of the Superconformal Index on RP^2xS^1
Abstract: We provide the exact formula and applications of the superconformal index for 3d N=2 supersymmetric field theories on an unorientable manifold RP^2xS^1. The index formula as a partition function can be exactly computed by the localization technique. As a physical application, we focus on using it to test the duality called 3d mirror symmetry. It is turned out that the Z_2 holonomy of RP^2 brings nontrivial phenomena on consistency to hold the duality. Further, the statement of this mirror symmetry on RP^2xS^1 is naturally generalized to nontrivial formulae of the q-analog of the hypergeometric function, which carries new perspectives into mathematical problems on the q-deformation. We additionally discuss mathematical aspects for the divergent series in the index formula regarding the connection problem and the q-Borel-Laplace transformation.


Date:May. 29, 2017 15:00pm
Speaker:Rui Dong Zhu (朱睿東) (University of Tokyo)
Title:Brane web in Ding-Iohara-Miki algebra and qq-characters.
Abstract: 5d AGT correspondence has a well-known simple and unified description by using the so-called Ding-Iohara-Miki (DIM) algebra, which is equipped with representations with Macdonald polynomials as basis. The topological vertex, which is an alternative and convenient tool to compute the Nekrasov partition function, was also embedded successfully into this algebra in the literature. In this talk, this embedding will first be reviewed and a direct generalization of the vertex will then be introduced. The qq-character, which was also derived in the vertical representation of DIM before, can be viewed as a commuting quantity with the T-operator whose VEV gives the partition function in this brane web picture. This agrees with Kimura-Pestun's result where the T-operator was identified with the screening charge of quiver W-algebra and the qq-character corresponded to the generator of such a W-algebra. We will give a map between the generator in DIM which gives rise to the qq-character and the representation theory of the A-type quiver Lie algebra as the main result. At last, if time is allowed, the subsequent work (work in progress) on generalization to D-type quivers, which might give a topological-vertex-like realization of the D-type quivers, will also be advertised.


(2016)


Date:Jan. 28, 2016 14:00pm
Speaker:吉田健太郎 (京都大学)
Title:古典的な弦の可積分性とカオス
Abstract: 近年、AdS/CFT対応における可積分性の研究に触発されて、 非可積分なAdS/CFT対応に強い関心が示されている。 AdS空間を変形したり、内部空間を球面以外のある種のコンパクトな 多様体に変えることによって、カオス的な振る舞いをする弦の古典解が現れる。 本講演では、弦の可積分性、古典カオスの基本的な性質の紹介からはじめ、 AdS5xT11におけるカオス的な弦について紹介する。 この古典カオスの存在によって示唆される今後のAdS/CFT対応 の研究の方向性についても議論したい。


(2015)


Date:Sep. 14, 2015
Speaker:Mareike Haberichter (U. of Kent)
Title:Squeezing Skyrmions
Abstract: We investigate the role of pressure in a generalised Skyrme model. We introduce pressure as the trace of the spatial part of the energy-momentum tensor and show that it obeys the usual thermodynamical relation. Then, we compute analytically the mean-field equation of state in the high and medium pressure regimes by applying topological bounds on compact domains. The equation of state is further investigated numerically for the charge one skyrmions. We identify which term in a generalised Skyrme model is responsible for which part in the equation of state. This is further compared with the Walecka model.


Date:Aug. 4, 2015 13:30pm
Speaker:橋本幸士 (大阪大)
Title:Speed Limit in Internal Space
Abstract: We find that motion in internal moduli spaces of generic domain walls has an upper bound for its velocity. Our finding is based on our generic formula for all-order effective actions of internal moduli parameter of domain wall solitons. We obtain, for generic domain walls, the effective Lagrangian is given by a function of the Nambu-Goto Lagrangian, which shows generically the existence of a speed limit in the internal space. The speed limit exists even for solitons in some non-relativistic field theories. (Based on the work in collaboration with Minoru Eto)


Date:May. 26, 2015 16:30pm
Speaker:大川博督 (早稲田大)
Title:箱の中での重力崩壊について
Abstract: 近年、Anti-de-Sitter(AdS)時空は重力崩壊に対して不安定であると指摘された。 漸近平坦時空とは異なり、漸近AdS時空上の摂動は単純に無限遠で減衰せずAdSの境界で反射される。 そして非線形相互作用の結果、波のエネルギーが高周波モードにカスケードしていきブラックホールが誕生するとされる。 しかしブラックホールに落ち着かないような初期条件のパラメータ領域も存在することが示され、 重力崩壊における系統的な理解が求められる。 本発表では、スカラー場の重力崩壊に関する簡単なレビューの後、そのような箱の役割や初期条件について議論したい。


Date:Apr. 27, 2015 16:30pm
Speaker:岡崎匡志 (KEK)
Title:Superconformal Quantum Mechanics from M2-branes
Abstract: We discuss the superconformal quantum mechanics arising from the M2-branes. We review the superconformal quantum mechanics and argue that conformal symmetry and supersymmetry in quantum mechanics contain a number of exotic properties which do not occur in higher dimensional field theories. We then review the M2-branes with a focus on the world-volume descriptions of the multiple M2-branes which are superconformal three-dimensional Chern-Simons matter theories. Combining the above two ingredients, we see that they may be connected in M-theoretical construction by considering the multiple M2-branes wrapped around a compact Riemann surface and study the emerging IR quantum mechanics. We also discuss possible applications of the superconformal quantum mechanics to mathematical physics.


Date:Apr. 20, 2015 16:30pm
Speaker:Antonino Flachi (Yamanashi Gakuin University)
Title:The chiral gap effect in curved space and some of its consequences
Abstract: I this talk we will introduce a new type of phenomenon occurring in interacting fermionic systems when lifted to curved space: the "Chiral Gap Effect". This phenomena is very general and it is related to the interplay between geometry and chiral symmetry. In QCD it suggests a decoupling of quark deconfinement near strongly gravitating sources, as black holes. After having introduced the phenomena in general, we will discuss what happens when external magnetic fields are present. In flat space, it is well known that this situation leads to the so called `magnetic catalysis'. We will show that when curvature and magnetic fields are simultaneously present, the way that the magnetic catalysis is activated changes and it is caused by geometrical terms, absent in flat space, leading to a new form of geometrically induced catalysis.


Date:Apr. 7, 2015 16:30pm
Speaker:Walter Vinci
Title:Quantum Annealing with Programmable Annealers
Abstract: Adiabatic quantum computation is a ground-state formulation of quantum computation that provides a higher level of protection against decoherence than any other circuit-based quantum algorithm. It thus possibly offers a promising route to the construction of a fault-tolerant quantum computer.Quantum annealing is a specific application of adiabatic quantum computation that promises to more efficiently solve optimization problems than other classical approaches. The D-Wave processors are a physical implementation of quantum annealing and are designed to solve for the ground state of Ising Hamiltonians on a hardware graph called ‘Chimera’. These processors have been the source of intense debate in the scientific community about the genuine “quantum” nature of their functioning. Attempting to resolve this issue is difficult because of the limited access that the “user” has at its disposal when programming the device (an initialization-readout only process). I will give an introduction to the basic concepts of adiabatic quantum computation and quantum optimization. I will also describe the D-Wave processors and their use, as well as summarize the state-of-the-art of our present knowledge on the physics of such devices. In the second part of my talk, I will describe my contribution to the topic, which involves experimental and theoretical investigations of the D-Wave devices. This includes the demonstration that D-Wave processors can be well-described by open system quantum dynamics, as well as the successful use of tailored error correction schemes.


Date:Mar. 11, 2015 16:30pm
Speaker:David Kubiznak (University of Waterloo)
Title:Black hole thermodynamics with pressuring Lambda
Abstract: The mass of a black hole has traditionally been identified with its energy. I describe a new perspective on black hole thermodynamics, one that identifies the mass of a black hole with chemical enthalpy, and the cosmological constant with thermodynamic pressure. This leads to an understanding of black holes from the viewpoint of chemistry, in terms of concepts such as Van der Waals fluids, reentrant phase transitions, and triple points.


(2014)


日時:2014年12月4日(木) 16:30
講演者:太田和俊 (明治学院大学)
タイトル:Exact Results in Quiver Quantum Mechanics and BPS Bound State Counting
概要: We exactly evaluate the partition function (index) of N=4 supersymmetric quiver quantum mechanics in the Higgs phase by using the localization technique. We show that the path integral is localized at the fixed points, which are obtained by solving the BRST equations, and D-term and F-term conditions. We turn on background gauge fields of R-symmetries for the chiral multiplets corresponding to the arrows between quiver nodes, but the partition function does not depend on these R-charges. We give explicit examples of the quiver theory including a non-coprime dimension vector. The partition functions completely agree with the mathematical formulae of the Poincare polynomials ($\chi_y$-genus) and the wall crossing for the quiver moduli spaces. We also discuss exact computation of the expectation values of supersymmetric (Q-closed) Wilson loops in the quiver theory.


日時:2014年11月27日(木) 16:30
講演者:疋田 泰章 氏 (立教大学)
タイトル:Higher spin AdS_3 holography and superstring theory
概要: 重力理論はスピン2のゲージ理論として記述することができるが、スピンを一般の場合に拡張したゲージ理論を考えることができる。 特に、超弦理論は質量をもってはいるが高いスピンの状態を数多く含んでおり、その質量のない極限に対応していると考えられている。また、 AdS/CFT対応への応用の観点でも、大きな発展を遂げてきている。高いスピンのゲージ理論のなかで最も有名なものとしてVasiliev理論 があるが、4次元のVasiliev理論は3次元のO(N)ベクトル模型と、3次元のVasiliev理論は2次元のラージNミニマル模型と双対 であると主張されている。さらに、Vasiliev理論において、場が行列に値をとるよう拡張された場合を考えることができる。4次元の場合は3 次元のAharony-Bergman-Jafferis (ABJ)理論と双対であり、超弦理論と直接的な関係がとりあげられている。ここでは、3次元の場合が2次元のコセット型の模型と双対であることを主張 し、その強い証拠をあげる。さらに、この場合における超弦理論との関連性を議論する。


日時:2014年9月25日(木) 16:30
講演者:阿武木啓朗氏 (工学院大/慶應大日吉物理)
タイトル:QCD相図における非一様カイラル/パイ凝縮の可能性
概要: QCD相図に空間非一様にカイラル対称性が破れた相が存在する可能性が指摘され ており、これまで 様々なアプローチから研究がなされている。これらの試みを簡単に紹介した後に、 カイラル臨界点を ミニマルに記述するギンツブルグ・ランダウ作用を用いて臨界点とその近傍に出 現する非一様状態、 その出現のメカニズム等について調べた結果について報告する。特に、現実的な 系で重要となる アイソスピン非対称性が臨界点と非一様状態に及ぼす効果について系統的な解析 を行った上で、 非一様な荷電パイ凝縮がQCD相図上に出現する可能性について指摘する。


日時: 7/3(THU.) 16:30 -
講師:Sven Bjarke Gudnason 氏
題目:Skyrmions and domain walls
概要:We will review the low-energy effective theory of mesons, in which baryons are realized as solitons, as introduced by Skyrme. Stability requires a fourth-order derivative term but any higher-order term can be used as well. Recent developments have focused on a type of model with a sixth-order term, which has received much interest due to that it possesses a BPS bound that can be saturated. In the first part of the talk we study the parameter space of such a theory. In the second part of the talk we will relate Skyrmions to baby-Skyrmions via a domain wall and study various configurations of such type. One particular type of configuration can possess a localized Skyrme charge on a "double domain wall", which does not require the presence of a higher-order derivative term. Such Skyrmion can in principle be realized in weakly coupled systems and perhaps in condensed matters systems.


日時: 6/4(WED.) 16:30 -
講師:小西 憲一 氏
題目:Monopole-vortex complex at large distances and NonAbelian duality-
概要:We discuss the large-distance approximation of the monopole-vortex complex soliton in a hierarchically broken gauge system, $SU(N+1) \to SU(N)\times U(1) \to {\bf 1}$, in a color-flavor locked $SU(N)$ symmetric vacuum. The ('t Hooft-Polyakov) monopole of the higher-mass-scale breaking appears as a point and acts as a source of the thin vortex generated by the lower-energy gauge symmetry breaking. The exact color-flavor diagonal symmetry of the bulk system is broken by each individual soliton, leading to nonAbelian orientational $CP^{N-1}$ zeromodes propagating in the vortex worldsheet, well studied in the literature. But since the vortex ends at the monopoles these fluctuating modes endow the monopoles with an unbroken local $SU(N)$ charge. This phenomenon is studied by performing the duality transformation in the presence of the $CP^{N-1}$ moduli space. The effective action is a 2D $CP^{N-1}$ model defined on a finite-width worldstrip.


日時: 4/14(MON.) 16:30 -
講師:Chris Lau 氏
題目:Construction and Quantisation of Skyrmions
概要:In this seminar, I will first give a brief introduction to the Skyrme model. Then, I will talk about the construction of approximate solutions of the Skyrme model using the rational map ansatz. The cubic grid method of constructing rational maps is discussed, and pictures of several new solutions is presented. In the second half of the seminar, the semi-classical quantisation of tetrahedrally-symmetric Skyrmions is discussed. Procedures of finding the allowed quantum states of the Skyrmions are mentioned. Using the cubic grid method, I will show that the allowed quantum states of all the tetrahedrally-symmetric Skyrmions constructed from the cubic grid can be classified into three sets.


日時: 3/12(WED.) 16:30 -
講師:Jarah Evslin 氏(Institute of High Energy Physics,China)
題目:Superconducting Abrikosov Vortices and the Arahanov-Bohm Effect
概要:I will review abelian and nonabelian vortices in the color-locked phases of gauge theories. In the presence of an additional weak gauge symmetry, the vortices exhibit a mini-Higgs mechanism, superconducting phases and an abelian or nonabelian Aharanov-Bohm effect.


(2013)


日時: 7/25(THU.) 16:30 -
講師:石井 貴昭 氏(Seoul National University)
題目:The gauge/gravity duality provides a handy toolkit for studying physics in strong couping. This has been applied to QCD and condensed matter physics, for instance. In this talk, we would like to discuss some topics on these subjects. For an application to QCD, we will discuss baryons in holographic QCD, particularly in the Sakai-Sugimoto model, where baryons are realized as solitons. In the Sakai-Sugimoto model, it has been accepted that some approximation could be employed for treating the baryon configuration according to an observation that the baryon size is very small. However, with this approximation, it has been shown that one does not reproduce a model-independent predictions for baryon electromagnetic form factors which are connected with long-range pion physics. We consider this problem without relying on the approximation, and show that the model-independent prediction is indeed obtained. On the other hand, for an application to condensed matter physics, we will focus on the holographic realization of superconductivity, and discuss impurity effects in this context. The simplest model for holographic superconductivity is an Abelian-Higgs model realizing the s-wave superconductivity, and we consider a generalized model where a massive vector field is coupled. We find that the mass gap in the optical conductivity is affected by the massive vector field: the exponential suppression of the excitations in the mass gap is replaced with a power-law one or while there is an enhancement depending on the vector mass.


日時: 5/27(Mon.) 16:30 -
講師: 三角 樹弘 氏(慶應義塾大学日吉物理学教室)
題目: QCD類似理論解析で迫る高エネルギー物理フロンティア
概要:強い相互作用を記述するSU(3)ゲージ理論 ? QCDは非摂動的解析が不可欠な理論であり、 その解析方法の模索は標準理論以後の素粒子物理学発展の原動力となってきた。 1つの大きな成功例は格子QCDであり、 近年では特にハドロン行列要素の計算を通して 標準理論パラメタの決定と新理論の絞り込みに貢献している。 そもそも電弱統一理論を含む素粒子標準理論全体が非可換ゲージ理論であり、 カイラルゲージ理論を含む非摂動解析法の確立はQCDの枠組みを越えて大きな重要性を持つ。 一方、標準理論を超える模型としてもQCD類似理論を内在する模型が多数提案されており、 今後はQCD解析で用いられてきた手法の応用が期待されている。 このトークでは非可換ゲージ理論が関わる素粒子物理の最前線を外観するとともに、 さまざまなQCD-like theories (Adj.-quark QCD、Super QCD、Twisted B.C.-QCD、高次元ゲージ理論) の解析結果とそれらが素粒子物理の理解にどのように繋がるのかを解説する。


日時: 4/22(Mon.) 16:30 -
講師: 坂井典佑 氏(慶應義塾大学日吉物理学教室)
題目: Stabilizing matter and gauge fields localized on walls
概要:Both non-Abelian gauge fields and minimally interacting massless matter fields are localized on a domain wall in the five-dimensional spacetime. Field-dependent gauge coupling naturally gives a position-dependent coupling to localize non-Abelian gauge fields on the domain wall. An economical field content allows us to eliminate a moduli for a instability, and to demonstrate the positivity of the position-dependent coupling in the entire moduli space. Effective Lagrangian similar to the chiral Lagrangian is found with a new feature of different coupling strengths for adjoint and singlet matter that depend on the width of the domain wall. (Ref: Masato Arai, Filip Blaschke, Minoru Eto, and Norisuke Sakai, arXiv:1303.5212)


日時: 2/26(Tue.) 16:30 -
講師: 森田 健 氏(高エネ研)
題目: Is “QGP=black hole” in string theory?
概要:There are a lot of works, in which the deconfinement (QGP) phase in the 4 dimensional pure Yang-Mills theory or QCD is studied by using gravities through holography. In most of these studies, a black hole (black brane) geometry is employed as the gravity dual of the QGP phase. However the correspondence between the QGP and black brane is a phenomenological relation and has not been verified. In this talk, we test this correspondence by studying string theory (Witten’s D4 brane holographic QCD model). We show that this correspondence is not correct in this model, and another geometry, which is not a black object, would correspond to the QGP phase. This result might suggest that we have to reconsider the previous studies in which the black branes are employed. In addition, we apply our result to the Sakai-Sugimoto model and propose a new mechanism for the chiral symmetry restoration at a finite temperature. (Reference arXiv:1207.4048)


日時: 1/29(Tue.) 16:30 -
講師: 古内 一之 氏(NCTS, Hsinchu)
題目: On high energy sensitivity of inflationary density perturbations
概要:I will discuss a possible naturalness issue/opportunity in inflationary density perturbations which arises from loop corrections.


日時: 1/28(Mon.) 15:00 -
講師: 村田 佳樹 氏(京大基研)
題目: ブラックホールの不安定性と局所ペンローズ不等式
概要:近年、超弦理論に動機付けられて多くの高次元ブラックホール解が発見されてきた。例えば、高次元に一般化されたSchwarzschild やKerr ブラックホール解が存在する。また、ドーナツの形をしたブラックリング解も見つかっており、高次元では無数のブラックホール解が存在することが示唆されて いる。では、高次元時空のダイナミクスの終状態として実現されるのはどのブラックホールであろうか?その疑問に答えるためには、高次元ブラックホールの安 定性性を調べる必要がある。また、AdS/CFT対応を用いると、ブラックホールの不安定性は双対理論の相転移に対応すると考えられており、安定性解析は 強結合ゲージ理論の相構造を知るための有効な手法になり得る。
本講演では、ブラックホール安定性解析の新しい手法について解説する。我々は、安定なブラックホールの初期摂動は局所ペンローズ不等式と呼ばれる、ある不 等式を満たすことを示した。言い換えれば、局所ペンローズ不等式の破れは不安定性の十分条件である。この不等式は、ブラックホールの初期摂動だけから評価 でき、摂動の時間発展を調べる必要はない。問題は初期面のconstraint 方程式を解くことのみに帰着されるので、ブラックホールの安定性解析を劇的に簡単化することができる。我々は、まずブラックストリング時空の不安定性をこ の手法で調べた。この時空は、あるコンパクト化の半径で安定性が入れ替わることが知られている。局所ペンローズ不等式の破れは、その知られている結果とほ ぼ同じコンパクト化の半径で起こることを確認した。次に、Myers-Perry ブラックホールを調べ、角運動量がある値より大きいときに、局所ペンローズ不等式が破れることを発見した。最後に、ブラックリング解を調べ、"fat" ring が不安定であることを示した。


日時: 1/28(Mon.) 16:30 -
講師: 山崎 加奈子 氏(東大駒場)
題目: PNJL模型によるクォーク-ハドロン相転移の記述
概要:QCD相転移の解析は重要な課題の一つである。有限温度QCDの起こす相転移のうち、本研究ではカイラル相転移と非閉じ込め相転移に着目する。カイ ラル相転移は、真空で自発的に破れたカイラル対称性が高温・高密度になって回復すること により起こる相転移である。非閉じ込め相転移は、カラー一重項状態だけが観測される閉じ込め相から、 温度の上昇によって閉じ込めが解消されることに伴う相転移であり、Polyakovループの期待値によって特徴づけられる。これらの相転移を経たQCD物 質をクォーク・グルーオン・プラズマ (QGP) と呼び、RHICやLHCにおける高エネルギー重イオン衝突実験からその生成が強く示唆されている。 有効模型を用いた相転移の解析はこれまでにも多く行われているが、カイラル対称性の自発的破れに基づいた有効模型の多くでは、閉じ込めの側面が捨象されて いる。QCDの有効模型として用いる以上、閉じ込め相ではクォークやグルーオンの自由度は現れず、バリオンが系を支配するという描像を記述できる模型が強 く望まれる。そこで本研究ではNambu-Jona-Lasinio model with Polyakov loop(PNJL模型)にクォークのcollective modeとしてメソン励起を取り込み、ゼロ密度で状態方程式を計算した。メソン励起を取り込む方法、温度の変化に伴う状態方程式の変化、メソンの状態方程 式への影響について紹介する。


(2012)


Date: 10/31(Wed.) 16:30 -
Speaker: Dr. Shin Nakamura(Kyoto University)
Title: Holographic Dual of Anomaly-induced Inhomogeneous Instability of Finite Density Systems
Abstract: Holography, or gauge/gravity duality, is a map between a strongly-interacting quantum gauge theory and a higher- dimensional gravity. This duality enables us to analyze non-perturbative properties of gauge theory in terms of gravity theory. We show that the Adler-Bell-Jackiw type anomaly may induce a spatially inhomogeneous instability of a gauge-theory plasma at finite density. This instability is mapped to an instability of a charged black hole owing to the Chern-Simons interaction of the electro-magnetic field on the black-hole geometry. I am going to show the basic idea and some detailed computation related to the instability in the gravity side.


Date: 10/19(Fri.) 17:00 -
Speaker: Dr. Sven Bjarke Gudnason (Hebrew U.)
Title: A quiver-like model realizing Natural SUSY
Abstract: Direct experimental searches for supersymmetric particles exclude light first generation squarks and gluinos while meson mixing requires the first and second generation to be almost degenerate. The third generation squarks should be as light as possible in order for supersymmetry to solve the (little) hierarchy problem. These two statements lead one to consider natural (or effective) supersymmetry; a model where the third generation of superpartners have small masses with respect to the first/second generation. Furthermore, the SM-like Higgs discovered at the LHC requires some extension of the MSSM or else the stops need to be heavier than 5 TeV. A quiver-like model is presented giving rise to SM-flavor structure, heavy first/second generation sfermions, a light third generation sfermions and finally the Higgs mass being increased by non-decoupled D-terms instead of extremely heavy stops. Explicit calculation reveal a somewhat heavy gaugini which in turn are able to "solve" the mu/Bmu problem. We apply limits from flavor physics and direct searches to evaluate how light a stop the model can provide. Further speculations on unification and improvements are discussed.


日時: 10/2(Tue.) 14:00 - (インフォーマルセミナー)
場所: 224教室(予定)
講師: 古城 徹 氏(Bielefeld University)
題目: Interweaving Chiral Spirals
概要: 近年、クォーク・マターにおける非一様なカイラル凝縮(カイラル密度波) の重要性が議論されている。実際に、典型的な有効モデルである NJL model な どで、 クォークの化学ポテンシャルが Lambda_QCD 程度の領域では、 一様なカイラル凝縮よりも非一様な凝縮の方が系の熱力学的エネルギーを 下げることが示されている。本講演では、非一様なカイラル凝縮の 発現機構を議論する。まず一次元の場合を例として示し、次に高次元系で 一次元系のアイデアをどのように応用できるかを議論する。 そして、複数のカイラル密度波が複数の方向にどのように系の中に 埋め込まれるかを論じて、QCDのような漸近的自由性を持つ理論では そのような結晶構造が可能であることを示す。 最後にカイラル密度波とバリオン密度の分布の関係性についても議論する。


日時: 10/1(Mon.) 16:30 -
講師: 古城 徹 氏(Bielefeld University)
題目: The nucleon axial charge as a source of chiral solitons
概要: Nucleon axial charge gA は核子ーπ 中間子の結合の強さを特徴付ける量であり、 核子多体系の記述において特別な役割を果たす。 この量を QCD の微視的記述の立場から理解しておくことは、実験データの乏しい 高密度核物質などに対する理論的指針を与えるうえで重要となる。 本講演では、核子内部におけるクォークのダイナミクスの観点から、 Nucleon axial charge gA をQCD の 1/Nc 展開の枠組みで議論する。 gA は核子を構成するクォークの波動関数に非常に敏感であることを示し、 核子の波動関数の候補となる複数の波動関数で比較する。 特に、ある特別なバリオン波動関数においてはカイラルソリトンとしてのバリオンが 自然に出て来るが、それがバリオンの基底状態としての核子となり得るか、 自然な核物質の描像を与えるかどうかについて議論する。


日時: 7/31(Tue.) 16:30 -
講師: 渡辺 悠樹 氏(UC, Berkeley)
題目: ローレンツ対称性がない場合の南部・ゴールドストーンボソンの統一 的記述
概要:1960年代に構築されて以来、南部・ゴールドストーンの定理は素粒子 物理学の基礎をなしてきた。系にローレンツ対称性があるときは、一般に南部・ ゴールドストーンボソンの数は破れた生成子の数dim(G/H)に一致する。 しかし近年活発に議論されている有限温度または有限密度の系のようにローレン ツ対称性がない場合には、南部・ゴールドストーン粒子の数が破れた生成子の数 より小さくなり、また低エネルギー極限での分散関係が線形ではなく二乗分散に なることがある。 今回我々は有効Lagrangianの方法を用いて、ローレンツ対称性がない場合の南 部・ゴールドストーンボソンの数や分散を統一的に説明することに成功したの で、これについて解説する。また時空の対称性の破れへの拡張についての最近の 進展についても議論したい。
参考文献:H. Watanabe, H. Murayama, Unified Description of Nambu-Goldstone Bosons without Lorentz Invariance, Phys. Rev. Lett. 108, 251602 (2012)


Date: 5/7(Mon.) 16:30 -
Speaker: Dr. Nan Su (Bielefeld Univ.)
Title: QCD thermodynamics at intermediate coupling
Abstract: The weak-coupling expansion of the QCD free energy is known to the order g^6*log[g], however, the resulting series is poorly convergent at phenomenologically relevant temperatures. In the first part of this talk, I will discuss how the gauge invariant hard-thermal-loop perturbation theory (HTLpt) reorganization of the calculation improves the convergence of the successive approximations to the QCD free energy. I will present HTLpt results of QCD thermodynamics to 3-loop order, which are consistent with lattice data down to 2-3T_c. This is a non-trivial result since, in this temperature regime, the QCD coupling constant is neither infinitesimally weak nor infinitely strong with g~2, or equivalently alpha_s~0.3. Therefore, we have a crucial test of the quasiparticle picture in the intermediate coupling regime. Our results suggest that HTLpt provides a systematic framework that could be used to calculate static and dynamic quantities for temperatures relevant at LHC. In the second part of this talk, I will move on to discuss the effect of the gauge fixing ambiguity, i.e. the Gribov copies, on the thermodynamic quantities. I will report the motivation and progress of a 1-loop Yang-Mills thermodynamics calculation with the Gribov copies fixed. The Gribov mass parameter can be solved self-consistently via a non-perturbative horizon condition and the result turns out to be of the order g^2T, i.e. the same order as the magnetic scale. As a consequence, the 1-loop thermodynamic potential already contains contributions from the non-perturbative magnetic scale. In contrast to the conventional Faddeev-Popov gauge fixing case where the vacuum part is discarded in the normalization, there are scale dependent divergences coming from the vacuum part which have to be regularized. As a result, fixing the Gribov copies may provide a perturbative scheme which is able to incorporate (part of) the non-perturbative magnetic contributions.


日時: 2/10(Fri.) 16:30 -
講師: 吉田 健太郎 氏(京大理)
題目: Hybrid integrable structure of deformed sigma models
概要: We show that Yangian x quantum affine symmetries are realized in two-dimensional sigma models with target spaces squashed spheres and warped AdS spaces. These symmetries allow two descriptions to describe its classical dynamics, according to the left and right symmetries. Each of the Lax pairs constructed in both ways leads to the same equations of motion. The two descriptions are related one another through a non-local map. We argue this equivalence also from the point of view of monodromy matrices.


日時: 1/25(Wed.) 13:00 -
講師: 竹内 宏光 氏(広島大)
題目: 2成分ボース・アインシュタイン凝縮体における流体力学的不安定性
概要: お互いに区別できる2種類の希薄ボース気体からなるボース・アインシュタイン凝縮体は、二つの複素秩序変数(巨視的波動関数)で記述され、2成分から成る 混相超流体を構成する。この混相超流体は原子間相互作用に依存して、相分離状態と二相混合状態に分類される。本講演では、この二つの状態における基本的な 流体力学的安定性とその不安定化ダイナミクスを紹介する。一つ目は、相分離状態におけるドメイン壁を挟んで超流体が相対速度をもつ状況を考え、流体力学に おけるケルビン・ヘルムホルツ不安定性との比較を見る。二つ目は、混ざり合った二成分超流体の対向流の不安定性を議論し、2成分量子渦糸タングル状態への 遷移ダイナミクスを説明する。


日時: 1/24(Tue.) 16:30 -
講師: 竹内 宏光 氏(広島大)
題目: 2成分ボース・アインシュタイン凝縮体におけるタキオン凝縮
概要: お互いに区別できる2種類の希薄ボース気体からなるボース・アインシュタイン凝縮体は、二つの複素秩序変数(巨視的波動関数)で記述され、2成分から成る 混相超流体を構成する。2種類の原子間斥力相互作用が十分大きい場合、2成分凝縮体は相分離を起こしてドメイン壁が安定に存在できる。本講演では、2成分 凝縮体におけるドメイン壁と反ドメイン壁の対消滅による不安定性と、超弦理論におけるDブレーンと反Dブレーンのタキオン凝縮との対応を議論する。このタ キオン凝縮では、量子渦(基本弦)が生成され、この現象が空間局在した相転移におけるドメイン壁形成の秩序化過程と見なし得ることを説明する。


(2011)


WORKSHOP

2nd International Workshop on Quarks and Hadrons under Extreme Conditions - Lattice QCD, Holography, Topology, and Physics at RHIC/LHC -
Date: 11/17 (Thu.) - 11/18 (Fri.)
Place: Raiosha 2F, Hiyoshi campus, Keio University
Program: PDF file


日時: 11/14(Mon.) 16:30 -
講師: 花田 政範 氏(Univ. of Washington)
題目: Relationship between QCD and QCD-like theories at finite density
概要: We argue that the whole or the part of the phase diagrams of QCD and QCD-like theories should be universal in the large-N_c limit through the orbifold equivalence. The whole phase diagrams, including the chiral phase transitions and the BEC-BCS crossover regions, are identical between SU(N_c) QCD at finite isospin chemical potential and SO(2N_c) and Sp(2N_c) gauge theories at finite baryon chemical potential. Outside the BEC-BCS crossover region in these theories, the phase diagrams are also identical to that of SU(N_c) QCD at finite baryon chemical potential. We also argue how large finite-N_c correction is expected. Our results strongly suggest that the chiral phase transition and the QCD critical point at finite baryon chemical potential can be studied using sign-free theories, such as QCD at finite isospin chemical potential, in lattice simulations.


Date: 11/9(Wed.) 16:30 -
Speaker: Prof. York Schroeder (Bielefeld Univ.)
Title: Quark mass effects in QCD thermodynamics
Abstract: Due to asymptotic freedom, QCD is guaranteed to be accessible to perturbative methods at asymptotically high temperatures. However, in 1979 Linde has pointed out the existence of an "infrared wall", beyond which an infinite number of Feynman diagrams contribute. This infrared problem can be overcome in the framework of dimensionally reduced effective theories, combining lattice measurements with lattice and continuum perturbation theory. Within this framework, I will discuss radiative corrections to how quark mass thresholds are crossed, as a function of the temperature, in basic thermodynamic observables - confirming the indication from leading order that the charm quark plays a visible role at surprisingly low temperatures.


日時: 10/17(Mon.) 16:30 -
講師: 佐藤 昌利 氏(東大物性研)
題目: トポロジカル超伝導体とマヨラナフェルミオン
概要: 従来、相構造の研究においては、自発的対称性の破れが重要な役割を果たしてきた。一方、自発的対称性の破れの概念ではとらえきれない量子相の存在も知られ ており、トポロジカル相と呼ばれている。本講演では、量子ホール状態、トポロジカル絶縁体などに代表されるトポロジカル相について簡単に説明した後、トポ ロジカル相にある超伝導状態であるトポロジカル超伝導体とその特徴的な励起であるマヨラナフェルミオンについて講演する。


Date: 8/29(Mon.) 16:30 -
Speaker: Prof. Kenichi Konishi (INFN, Pisa & Pisa U.)
開催場所: 慶應義塾大学日吉キャンパス第2校舎224番教室 (普段と異なるので注意!)
Title: The monopole-vortex complex: dual gauge symmetry from flavor
Abstract: The idea that the dual gauge symmetry of nontrivial type (i.e., non-Abelian) is a new manifestation of the global flavor symmetry, seems to be gaining familiarity, if not yet properly understood. The main issue is the subtle interplay between the strong gauge dynamics involving various soliton-like excitations and the global symmetry. We discuss, in an attempt to go into the heart of the problem, monopole-vortex complex solitonlike configurations arising in hierarchically broken gauge systems, G → H → 1, taking as a concrete model the softly-broken N=2 supersymmetric Quantum Chromodynamics. Our consideration involves also the rich results on the non-Abelian-vortex moduli obtained in the last few years, as well as some old and more recent results about non-Abelian monopoles. There is in fact a clear indication how the dual gauge symmetry arises from flavor in the r-vacua of the softly-broken N=2 susy QCD. If realized in the real world QCD, this kind of mechanism would explain why the chiral symmetry breaking and confinement appear to be interlocked.


Date: 7/20(Wed.) 13:30 -
Speaker: Dr. Marco Ruggieri (YITP)
Title: Exploring QCD with a chiral chemical potential
Abstract: I discuss the phase structure of QCD with a chiral chemical potential, which represents a sign-free theory whose interest is related both to the phenomenology of heavy ion collisions (mainly to the chiral magnetic effect) and to the theory (mainly, to the possibility of performing simulations of grand canonical ensembles).


日時: 6/20(Mon.) 16:30 -
講師: 大河内 豊 氏(IPMU)
題目: Constraints on Direct Gauge Mediation Models
概要: 近年注目されている超対称性の破れのモデルをもとに、宇宙論的な観測からくる 制限をついて議論する。特にISSモデルをもとに構成したダイレクト型のゲージ メディエーションモデルについてコスミックストリングからくる制限を紹介する。


日時: 5/30(Mon.) 16:30 -
講師: 今村 洋介 氏(東京工業大学)
題目: Exact results in 3d gauge theories and M-theory
概要: 近年、局所化と呼ばれる方法を用いることで、超対称ゲージ理論の分配関数やインデックスが厳密に計算された。このセミナーでは、3次元ゲージ理論のイン デックスの公式の導出方法を紹介する。また、いくつかの3次元超対称Chern-Simons理論のインデックスをlarge N 極限において計算した結果をAdS_4/CFT_3の予言と比較することで、AdS_4/CFT_3の非自明なチェックを行う。


日時: 5/16(Mon.) 16:30 -
講師: 疋田 泰章(慶應義塾大学)
題目: The FZZ duality with boundary -- D1-branes in 2d black hole and their dual
概要: The Fateev-Zamolodchikov-Zamolodchikov (FZZ) duality relates Witten's 2d black hole and sine-Liouville theory. Sine-Liouville theory describes the condensation of closed string tachyon winding over a cylinder. The FZZ duality states that the tachyon condensation deforms the cylinder geometry to the cigar (Euclidean 2d black hole) geometry. In our previous work, we have proven the duality for sphere amplitudes and generalized to the case with closed Riemann surface of arbitrary genus. In this talk, we extend the duality to disk amplitudes. More specifically, we relate D1-branes in the cigar model to D2-branes in the sine-Liouville theory.
参考文献:arXiv:1012.4731 [hep-th]


Date : 2/28(Mon.) 16:30 -
Speaker: Dr. Walter Vinci(Univ. of Minnesota)
Title: Non-Abelian Monopoles in the Higgs Phase
Abstract: We use the moduli matrix approach to study the moduli space of 1/4 BPS kinks supported by vortices in the Higgs phase of N = 2 supersymmetric U(N) gauge theories when non-zero masses for the matter hypermultiplets are introduced. We focus on the case of degenerate masses. In these special cases vortices acquire new orientational degrees of freedom, and become "non-Abelian". Kinks acquire new degrees of freedom too, and we will refer to them as "non-Abelian". As already noticed for the Abelian case, non-Abelian kinks must correspond to non-Abelian monopoles of the unbroken phase of SU(N) Yang-Mills. We show, in some special cases, that the moduli spaces of the two objects are in one-to-one correspondence. We argue that the corre- spondence holds in the most general case. The consequence of our result is two-fold. First, it gives an alternative way to construct non-Abelian monopoles, in addition to other well- known techniques (Nahm transform, spectral curves, rational maps). Second, it opens the way to the study of the quantum physics of non- Abelian monopoles, by considering the simpler non-Abelian kinks.
Reference:arXiv:1012.4057 [hep-th]


Date : 1/24(Mon.) 16:30 -
Speaker: Dr. Antonino Flachi(YITP)
Title: Four-fermion effective theories in curved space at finite temperature and density
Abstract: The aim of this talk is to present a new formalism that allows to deal with four-fermion effective field theories at finite temperature and density in curved and flat space. The formalism is based on the use of the effective action and zeta function regularization, and supports the inclusion of inhomogeneous and anisotropic phases. One of the key points of the method is the use of a non-perturbative ansatz for the heat-kernel that returns the effective action in partially resummed form, providing a way to go beyond the approximations based on the Ginzburg-Landau expansion for the partition function. The effective action for the case of ultra-static Riemannian spacetimes is discussed in general. A series representation, valid when the chemical potential satisfies a certain condition, and a more general expression for the effective action, valid for arbitrary values of the chemical potential, are presented. We finally present a sample application, and show how the formalism can be used to discuss the formation of inhomogeneous phases in the case of static Einstein spaces and illustrate how numerical implementations of the method can be done.


(2010)


日時: 11/29(Mon.) 16:30 -
講師: 太田 和俊 氏(明治学院大学)
題目: Volume of Moduli Space of Vortices and Localization Formula
概要: We evaluate volume of moduli space of BPS vortices on a compact Riemann surface by using topological field theory and localization formula developed by Moore, Nekrasov and Shatashvili. We apply this technique to Abelian (ANO) vortex and show that the volume of moduli completely agrees with the previous results by Manton et al. We extend our evaluation to non-Abelian gauge group and multi flavors. We also compare our result with a volume of the Hanany-Tong moduli space.


日時: 11/15(Mon.) 16:30 -
講師: 岡澤 晋 氏(高エネルギー加速器研究機構)
題目: Black Holes and the Fluctuation Theorem
概要: We investigate non-equilibrium nature of fluctuations of black hole horizons by applying the fluctuation theorem developed in the non-equilibrium statistical physics. The theorem applied to space-times with black hole horizons reveals a violation of the generalized second law of thermodynamics. In this talk, after introducing the fluctuation theorem, we show that some characteristics of the Fokker-Planck equation which describes non-equilibrium dynamics of black hole horizons and matters.
参考文献:arXiv:1008.1184 [gr-qc]


日時:: 10/25(Mon.) 16:30 -
講師: 酒井 一博 氏 (慶應義塾大学)
題目: Gluon scattering amplitudes and thermodynamic Bethe ansatz equations
概要: Alday and Maldacena proposed a method of computing gluon scattering amplitudes in N=4 super Yang-Mills at strong coupling by using the AdS/CFT correspondence. The amplitude is given by the area of a minimal surface in AdS_5 with a null polygonal boundary. Recently, it turned out that minimal surfaces corresponding to the general n-point amplitudes are characterized in terms of a sort of Thermodynamic Bethe Ansatz (TBA) equations. After reviewing the general TBA description, we focus on the case of n=6 and analyze the solution in detail. We explain how to solve the TBA equations perturbatively and compute the amplitude by making use of the underlying integrable model.
参考文献: arXiv:0911.4708 [hep-th], arXiv:1002.2459 [hep-th], arXiv:1002.2941 [hep-th] arXiv:1005.4487 [hep-th]


慶應義塾大学 日吉物理学教室 (Department of Physics, Hiyoshi Campus, Keio University)
慶應義塾大学 素粒子論グループ (High Energy Theory Group, Keio University)