Masaki Shigemori, Nagoya University
A Holographic Study of Thermalization in Strongly Coupled Plasmas
Meeting room 1, Kenkyu honkan 1F
Using the AdS/CFT correspondence, we probe the scale-dependence of thermalization in strongly coupled field theories following a quench via saddlepoint calculations of 2-point functions, Wilson loops and entanglement entropy in d=2,3,4. For homogeneous initial conditions, the entanglement entropy thermalizes slowest, and sets a timescale for equilibration that saturates a causality bound. In this strongly coupled setting, the UV thermalizes first.
Kazunori Kohri, KEK
[理論宇宙物理グループセミナー] 速度依存する対消滅散乱断面積をもつダークマターモデルの宇宙論的検証
Meeting room 3, Kenkyu honkan 1F ２００８年秋から２００９年春にかけてPAMELA衛星とFermi衛星により、宇宙線の陽電子・電子が標準的な宇宙物理学の理論予想より過剰に検出されたと報告されました。それに対し、素粒子論的な興味ではダークマターの対消滅による陽電子・電子生成のモデルが多数考案されてきた。観測された陽電子・電子過剰を説明するために必要な散乱断面積の値は、熱浴から作られて現在に残るダークマターの量を説明するために必要な散乱断面積の値より、１０００倍も大きく、その比の値はブーストファクターと呼ばれている。
２００８年秋から２００９年春にかけてPAMELA衛星とFermi衛星により、宇宙線の陽電子・電子が標準的な宇宙物理学の理論予想より過剰に検出されたと報告されました。それに対し、素粒子論的な興味ではダークマターの対消滅による陽電子・電子生成のモデルが多数考案されてきた。観測された陽電子・電子過剰を説明するために必要な散乱断面積の値は、熱浴から作られて現在に残るダークマターの量を説明するために必要な散乱断面積の値より、１０００倍も大きく、その比の値はブーストファクターと呼ばれている。
今回のセミナーでは、そのように大きなブーストファクターを出す可能性のある速度依存する散乱断面積が、いかに宇宙論的に影響を及ぼし、他の観測から厳しく制限されるかについて解説します。
Naoki Yamatsu, Kyushu University
Chiral Generations in Vectorlike Model with Noncompact Horizontal Symmetry
Meeting room 1, Kenkyu honkan 1F
One of the most remarkable features in Nature is the existence of three generations of chiral quarks and leptons and these mass hierarchy. To understand the particle properties, I have been studying the supersymmetric vectorlike model with a noncompact group horizontal symmetry. The model has two aspects: (1) Three chiral generations emerge as a result of spontaneous breaking of the horizontal symmetry in the vectorlike model. (2) The structure of Yukawa couplings is constrained by the horizontal symmetry and become hierarchical naturally. In this talk, I will mainly discuss the above two characters. I will also introduce some other aspects of the model.
Hideo Kodama, KEK
[理論宇宙物理グループセミナー] Introduction to the toric CY compactification
Meeting room 3, Kenkyu honkan 1F 最近，ヘテロ型超弦理論（M理論）で標準モデルを再現しつつモジュライ安定化を実現するモデルの構成法として，Calabi-Yau多様体のトーリック構成とその上のモナードベクトルバンドルが注目されている．この方法の基本アイデアとその背景を（この分野の素人として勉強した範囲で）紹介する．
最近，ヘテロ型超弦理論（M理論）で標準モデルを再現しつつモジュライ安定化を実現するモデルの構成法として，Calabi-Yau多様体のトーリック構成とその上のモナードベクトルバンドルが注目されている．この方法の基本アイデアとその背景を（この分野の素人として勉強した範囲で）紹介する．
参考文献：
E. Witten: “Strong coupling expansion of Calabi-Yau compactification”, NPB471:135 (1996)
M. Kreuzer: “Toric Geometry and Calabi-Yau Compactifications”, hep-th/0612307.
Seung-Joo Lee: “Combinatorics in N = 1 Heterotic Vacua”, arXiv:1105.3462
Lara B. Anderson, James Gray, Andre Lukas, Burt Ovrut: “Stabilizing All Geometric Moduli in Heterotic Calabi-Yau Vacua”, arXiv:1102.0011
Ken'ichiro Nakazato, Tokyo University of Science
Exploring Hadron Physics in Black Hole Formations: a New Promising Target of Neutrino Astronomy
Room 345, 4 go-kan
Recently, we have performed several sets of core-collapse simulation of a non-rotating star with 40Msolar by a general relativistic neutrino-radiation-hydrodynamics code so as to compute quantitatively the dynamics up to the black hole formation as well as the neutrino luminosities and spectra. Employing different hadronic equations of state (EOS), we have demonstrated that the duration of neutrino emissions from this event is sensitive to the stiffness of EOS at supra-nuclear densities and, therefore, that the observation of neutrinos from such an event will provide us with valuable information on the properties of dense and hot hadronic matter. While this approach can not distinguish EOS’s with a similar stiffness: a soft nucleonic EOS and a hyperonic EOS, for example, we find that we can break this degeneracy by analyzing more in detail the time variation of neutrino numbers observed at a terrestrial detector. Performing the Kolmogolov-Smirnov test, which is free from the ambiguity of the distance to the progenitor, we show that the break-up of the degeneracy of hadronic EOS’s is indeed feasible for Galactic events. Ref. Nakazato et al. Physical Review D 81 (2010) 083009
Thomas Durt, Institut Fresnel, Marseille
Fundamental aspects of Time in Quantum Mechanics and Meson Phenomenology
Seminar room, Kenkyu honkan 3F
Mesons illustrate fundamental quantum properties such as the superposition principle (for instance in kaon oscillations), and their phenomenology also appeared very useful in the past for measuring CP-violation related effects. More recently, mesons were also useful for testing decoherence and entanglement related effects. The aim of our talk is to show that mesons could also be useful for revealing and/or studying fundamental aspects of Time in the quantum theory, such as the existence of a Time Operator (and also of the so-called Time Superoperator).
Naoki Yoshida, IPMU
初期宇宙での構造形成: はじめの３億年
Meeting room 1, Kenkyu honkan 1F
最近の大型望遠鏡を用いた観測により、赤方偏移8以上、つまりビッグバン後数億年の頃の銀河やガンマ線バーストが捉えられました。マイクロ波背景放射の偏光観測などから示唆される宇宙再電離の時期と合わせ、宇宙早期に星や銀河が数多く形成されたと判明しました。私たちの研究グループは、標準宇宙モデルに基づいた大規模数値シミュレーションを行い、初代星や初代ブラックホールの形成過程の研究を行ってきました。その成果を発表します。これからの銀河、ガンマ線バースト、中性水素の観測によりどのようなことが明らかになると期待されるのか展望を述べます。
Tomo Takahashi, Saga Universtity
Probing the early Universe with isocurvature fluctuations and non-Gaussianity
Meeting room 1, Kenkyu honkan 1F I discuss primordial fluctuations and its non-Gaussianity in models with isocurvature perturbations. First I describe a general formalism which can give a systematic calculation of non-linear perturbations in models with isocurvature fluctuations. Then I discuss isocurvature fluctuations and non-Gaussianity in the mixed curvaton and inflaton model where the curvaton and the inflaton are both responsible for cosmic density fluctuations. The issue of differentiating CDM and baryon isocurvature modes using 21 cm fluctuations is also briefly discussed.
I discuss primordial fluctuations and its non-Gaussianity in models with isocurvature perturbations. First I describe a general formalism which can give a systematic calculation of non-linear perturbations in models with isocurvature fluctuations. Then I discuss isocurvature fluctuations and non-Gaussianity in the mixed curvaton and inflaton model where the curvaton and the inflaton are both responsible for cosmic density fluctuations. The issue of differentiating CDM and baryon isocurvature modes using 21 cm fluctuations is also briefly discussed.
References: D. Langlois, T. Takahashi, arXiv:1012.4885 M. Kawasaki, T. Sekiguchi, T. Takahashi, arXiv:1104.5591
Makoto Nozawa, KEK
[理論宇宙物理グループセミナー] Black holes in an expanding universe
Meeting room 3, Kenkyu honkan 1F Black holes in the isolated and stationary spacetimes have been intensively studied so far. They are completely characterized by conserved charges and exhausted by Kerr family. Black holes in non-isolated and dynamical background, on the other hand, have been less understood. In particular, the black-hole spacetime which is asymptotically FLRW universe is of considerable importance when discussing formation and evaporation of primordial black holes. In this talk, I will give a talk on the study of `black hole candidate’ recently obtained by Ohta et al, which is specified by a set of harmonic functions. We established that this geometry indeed describes a black hole in a decelerating FLRW universe satisfying appropriate physical conditions. This solution can be generalized to a universe with an arbitrary power law expansion and to any number of spacetime dimensions. Furthermore, we show that in five dimensions this solution is pseudo-supersymmetric in fake supergravity coupled to arbitrary number of scalars and gauge fields. We discuss physical properties and causal structures in detail.
Black holes in the isolated and stationary spacetimes have been intensively studied so far. They are completely characterized by conserved charges and exhausted by Kerr family. Black holes in non-isolated and dynamical background, on the other hand, have been less understood. In particular, the black-hole spacetime which is asymptotically FLRW universe is of considerable importance when discussing formation and evaporation of primordial black holes. In this talk, I will give a talk on the study of `black hole candidate’ recently obtained by Ohta et al, which is specified by a set of harmonic functions. We established that this geometry indeed describes a black hole in a decelerating FLRW universe satisfying appropriate physical conditions. This solution can be generalized to a universe with an arbitrary power law expansion and to any number of spacetime dimensions. Furthermore, we show that in five dimensions this solution is pseudo-supersymmetric in fake supergravity coupled to arbitrary number of scalars and gauge fields. We discuss physical properties and causal structures in detail.
参考文献：Kei-ichi Maeda & Masato Nozawa, Phys.Rev. D81 (2010) 124038; D83 (2011) 024018
Sergey Ketov, Tokyo Metropolitan University
Cosmological Inflation in Supergravity: The Meeting Point of Cosmology and High-Energy Physics
Meeting room 3, Kenkyu honkan 1F
