## Seminars in 2013

Seminars from April 2013 through March 2014.

EHQG Seminar

- Title
- What's wrong with Goldstone?
- Speaker
- Hitoshi Murayama (KIPMU, Univ. Tokyo)
- Date & Time
- Monday, March 24, 2014, 2:00 p.m.
- Place
- Science Symposia (ES635)
- Abstract
- Spontaneous Symmetry Breaking is a very universal concept applicable for a wide range of subjects: crystal, superfluid, neutron stars, Higgs boson, magnets, and many others. Yet there is a variety in the spectrum of gapless excitations even when the symmetry breaking patterns are the same. We unified all known examples in a single-line Lagrangian of the low-energy effective theory. In addition, we now have a better understanding of what happens with space-time symmetries, and predict gaps for certain states exactly based on symmetries alone.

QG Seminar

- Title
- Collapse of a massive field in asymptotically flat spacetimes
- Speaker
- Hirotada Okawa (CENTRA, IST, Lisbon)
- Date & Time
- Tuesday, February 25, 2014, 2:00 p.m.
- Place
- QG-Lab Colloquium Room (ES744)
- Abstract
- It was recently pointed out that anti-de Sitter (AdS) spacetime is unstable against gravitational collapse. The perturbation in AdS does not simply decay away and can be reflected by AdS boundary to nonlinearly interact with one another. Confinement would play an important role in the nonlinear, turbulent instability. On the other hand, massive fundamental fields can also provide low-frequency confinement as we will touch on our study of “Black Hole Bomb/Superradiant instability” around the rotating BH. Thus, we revisit an old problem on collapse of massive fields. In this presentation, we will show the collapse after successive reflections by the potential wall even in asymptotically flat spacetimes and discuss how the field collapses to a BH.

EHQG Seminar

- Title
- Core-Collapse Supernovae and Neutrinos
- Speaker
- Hideyuki Suzuki (Tokyo Univ. of Sci.)
- Date & Time
- Tuesday, February 18, 2014, 5:00 p.m.
- Place
- Science Symposia (ES635)
- Abstract
- In this talk I will review the current status of researches on core-collapse supernova explosions. They are very complicated phenomena including stellar evolutionary models, general relativistic hydrodynamics, nuclear equation of states, and neutrino physics and so on. Recent development of numerical simulations and newly constructed supernova neutrino database for various supernova models will be also presented.

QG Seminar

- Title
- ブラックストリング不安定性と流体・重力対応
- Speaker
- Umpei Miyamoto (APU)
- Date & Time
- Monday, February 17, 2014, 3:00 p.m.
- Place
- QG-Lab Colloquium Room (ES744)
- Abstract
- ブラックホール熱力学は定常なブラックホールが熱力学系と対応していることを教えてくれるが，動的なブラックホールが同様の対応物をもつかは長年の謎であった．この問題に一つの解答を与えるのが，近年注目を集めている流体・重力対応である．本講演では，ブラックストリングと呼ばれる高次元ブラックホールの不安定性（Gregory-Laflamme不安定性）を切り口として，ブラックホールと流体の類似点や流体・重力対応について解説したい．

EHQG Seminar

- Title
- Vortices and other topological solitons in dense quark matter
- Speaker
- Muneto Nitta (Keio Univ.)
- Date & Time
- Tuesday, February 4, 2014, 5:00 p.m.
- Place
- Science Symposia (ES635)
- Abstract
- Dense quantum chromodynamic matter accommodates various kind of topological solitons such as vortices, domain walls, monopoles, kinks, boojums, and so on. In this talk, we discuss various properties of topological solitons in dense QCD and their phenomenological implications. Particular emphasis is placed on the topological solitons in the color–flavor-locked (CFL) phase, which exhibits both superfluidity and superconductivity. The most fundamental string-like topological excitations in the CFL phase are non-Abelian vortices, which are 1/3 quantized superfluid vortices and color magnetic flux tubes. These vortices are created at a phase transition by the Kibble–Zurek mechanism or when the CFL phase is realized in compact stars, which rotate rapidly. Bosonic and fermionic zero-energy modes are trapped in the core of a non-Abelian vortex and propagate along it as gapless excitations. As a remarkable consequence of Majorana fermion zero modes, non-Abelian vortices are shown to behave as a novel kind of non-Abelian anyon. Ref. M. Eto, Y. Hirono, M. Nitta and S. Yasui, PTEP 2014 1, 012D01 [arXiv:1308.1535].

QG Seminar

- Title
- First quantized theory of expanding universe from field quantization in mini-superspace
- Speaker
- Daisuke Ida (Gakushuin Univ.)
- Date & Time
- Monday, February 3, 2014, 2:00 p.m.
- Place
- QG-Lab Colloquium Room (ES744)
- Abstract
- Einstein重力のHamilton形式は拘束系であり，Hamiltonianが拘束函数であるために時間発展を定義できない。形式的には特殊相対論における自由粒子のHamilton形式に似ており，実際に空間のRiemann計量を一般化座標とする配位空間上の自由粒子の運動と見ることができる。このことから，配位空間上の場の理論を考えることが古くから考えられており，一般に第3量子化とよばれる。ただし，この配位空間の幾何学的構造について言えることはほとんどなく，時空のクラスを限ることにより自由度を有限個にしたmini-superspace modelで議論することになる。通常，一様等方宇宙に対するmini-superspace modelにおける第3量子化は無限個の宇宙の生成という結果になる。これは配位空間の時間依存性により，場の量子状態を記述するHilbert空間が可分でなくなるからである。今回は，flatまたはopenな宇宙に対してはHilbert空間にベクトル束の構造を入れることにより，1つの宇宙の量子状態を記述できる量子論をつくることができることを説明する。

EHQG Seminar

- Title
- Electroweak Baryogenesis beyond the high temperature expansion
- Speaker
- Ran Huo (KIPMU, Univ. Tokyo)
- Date & Time
- Tuesday, January 28, 2014, 5:00 p.m.
- Place
- Science Symposia (ES635)
- Abstract
- I will talk about some new way to get a strongly first order phase transition in electroweak baryogenesis. Traditionally the phase transition is estimated by the high temperature expansion of the finite temperature potential, in which at leading order no contribution from fermions is seen. The new way is directly seen as a jump on the finite temperature JB JF curves. Contributions from the fermions are also get, which is comparable to the contribution of bosons, and with supersymmetric protection of the Higgs quartic coupling running the model can be tuned. We talk about two models, one is designed for Higgs diphoton decay enhancement, the other is a vector like new generation model.

QG Seminar

- Title
- 低速中性子を用いた短距離重力の研究
- Speaker
- Hirohiko Shimizu (Nagoya Univ.)
- Date & Time
- Monday, January 27, 2014, 2:00 p.m.
- Place
- QG-Lab Colloquium Room (ES744)

EHQG Seminar

- Title
- Dynamical Meson Melting in Holography
- Speaker
- Shunichiro Kinoshita (OCAMI)
- Date & Time
- Tuesday, January 21, 2014, 5:00 p.m.
- Place
- Science Symposia (ES635)
- Abstract
- We discuss mesons in thermalizing gluon backgrounds in the N=2 supersymmetric QCD using the gravity dual. We numerically compute the dynamics of a probe D7-brane in the Vaidya-AdS geometry that corresponds to a D3-brane background thermalizing from zero to finite temperatures by energy injection. In static backgrounds, it has been known that there are two kinds of brane embeddings where the brane intersects the black hole or not. They correspond to the phases with melted or stable mesons. In our dynamical setup, we obtain three cases depending on final temperatures and injection time scales. The brane stays outside of the black hole horizon when the final temperature is low, while it intersects the horizon and settles down to the static equilibrium state when the final temperature is high. Between these two cases, we find the overeager case where the brane dynamically intersects the horizon although the final temperature is not high enough for a static brane to intersect the horizon. The interpretation of this phenomenon in the dual field theory is meson melting due to non-thermal effects caused by rapid energy injection.

EHQG Seminar

- Title
- Propagators in nonstationary spacetimes and a nonequilibrium-thermodynamic character of de Sitter space
- Speaker
- Yuho Sakatani (Kyoto Sangyo Univ.)
- Date & Time
- Tuesday, January 14, 2014, 5:00 p.m.
- Place
- Science Symposia (ES635)
- Abstract
- In the first half of this talk, we discuss an issue of defining a vacuum state of a quantum field theory in a spacetime with no global timelike Killing vector. We propose to take the vacuum as the instantaneous ground state at each moment and develop a framework to calculate various Green's functions for such vacua. In the second half, on the basis of the above framework, we reveal a nonequilibrium-thermodynamic character of de Sitter space. We first introduce an Unruh-DeWitt detector interacting with a scalar field in the instantaneous 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 de Sitter radius. This relaxation time gives an example of nonequilibrium-thermodynamic quantities intrinsic to de Sitter space. References: M. Fukuma, Y. Sakatani and S. Sugishita, “Propagators in de Sitter space” [PRD88 (2013) 024041, arXiv:1301.7352] “Master equation for the Unruh-DeWitt detector and the universal relaxation time in de Sitter space” [arXiv:1305.0256]

EHQG Seminar

- Title
- QCD at Finite Density and Sign Problem
- Speaker
- Keitaro Nagata (KEK)
- Date & Time
- Tuesday, December 17, 2013, 5:00 p.m.
- Place
- Science Symposia (ES635)
- Abstract
- Properties of QCD at finite temperatures and densities have attracted attention owing to a non-trivial nature of QCD and potential applications to some kinds of matters existing in nature, such as nuclei, quark-gluon plasma, high-dense matter inside neutron stars. This topics has known to be difficult because of the sign problem in lattice QCD at finite densities, and efforts have been made to deal with the sign problem. In this talk, we study properties of QCD at finite temperatures and densities in lattice QCD. We introduce a technique providing a precise way to deal with the effect of chemical potential. Applying the technique, we investigate thermodynamical quantities, and phase transitions between confinement/deconfinement phases. Then, we calculate baryon number distributions, which describe a probability of microstates with a fixed baryon number, in connection with new experiments performed at RHIC.

QG Seminar

- Title
- 時空の隠れた対称性に関する最近の進展について
- Speaker
- Tsuyoshi Houri (Rikkyo Univ.)
- Date & Time
- Monday, December 16, 2013, 2:00 p.m.
- Place
- QG-Lab Colloquium Room (ES744)
- Abstract
- よく知られているように、時空の対称性はキリングベクトルとよばれるベクトル場によって記述される。一方、テンソル場によって記述される対称性は時空の隠れた対称性とよばれ、ブラックホール時空の研究において重要な役割を果たしてきた。本講演では、カーブラックホール時空における隠れた対称性のレビューから始め、その高次元ブラックホール時空への拡張について紹介する。また、隠れた対称性を持つ時空の一般的性質についても概説する。後半に、時空の隠れた対称性に関する最近の進展や残されている課題、今後の展望について話したい。

EHQG Seminar

- Title
- Localized features in the primordial spectra: signatures of heavy physics?
- Speaker
- Ryo Saito (YITP, Kyoto Univ.)
- Date & Time
- Tuesday, December 3, 2013, 5:00 p.m.
- Place
- Science Symposia (ES635)
- Abstract
- Primordial density fluctuations provide one of a few ways to probe the inflationary era. Although an inflationary model generally has a number of scalar degrees of freedom, in the standard approach, the spectra of the primordial density fluctuations are evaluated neglecting heavy modes, whose masses are larger than the Hubble scale of inflation. It was, however, pointed out recently that the heavy modes can affect the fluctuations when the background trajectory is curved in the field space. A turn in the trajectory can induce localized features in the primordial spectra through two mechanisms: mode mixing and resonance. In this talk, we investigate how large features can be induced through a turn and find relation between the features by the mode mixing and resonance.

EHQG Seminar

- Title
- Non-Abelian flux tubes and confined monopoles in high density QCD
- Speaker
- Minoru Eto (Yamagata Univ.)
- Date & Time
- Tuesday, November 19, 2013, 5:00 p.m.
- Place
- Science Symposia (ES635)
- Abstract
- Topological solitons of QCD, magnetic monopoles and flux tubes, have been considered as a clue to the long standing confinement problem. However, it is hard to analytically solve the problem because of the asymptotic freedom of QCD at low energy. On the other hand, QCD becomes weak coupling at high baryon density limit. Interestingly, high density QCD has a similar symmetry structure as low density QCD, where there exist various topological solitons. Especially, I will concentrate on color-magnetic flux tubes, and magnetic monopoles which can be demonstrated in a well defined manner to be confined and form a mesonic state due to the color superconductivity. I will also explain another type of non-Abelian vortices which is related to the chiral symmetry breaking at high density QCD.

EHQG Seminar

- Title
- Fuzzy Objects in Noncommutative Geometry and Their Applications to Gravity
- Speaker
- Shinpei Kobayashi (Gunma Natl. Coll. Tech.)
- Date & Time
- Tuesday, November 12, 2013, 5:00 p.m.
- Place
- Science Symposia (ES635)
- Abstract
- In this talk, I would like to discuss on some fuzzy objects in noncommutative geometry and their applications to field theories and gravity. For example, the fuzzy disc, which is a (2+1)-dimensional, circular region in a noncommutative plane (the Moyal plane) can be used to obtain nontrivial solutions in field theories on a noncommutative space and the fuzzy versions of some solutions in Einstein gravity. I also refer to an interesting relation between fuzzy objects and the laser physics.

EHQG Seminar

- Title
- Universality in quantum few-body physics
- Speaker
- Yusuke Nishida (Tokyo Inst. Tech.)
- Date & Time
- Tuesday, October 29, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- Physics is said to be universal when it emerges regardless of the underlying microscopic details. A prominent example is the Efimov effect, which predicts the emergence of an infinite tower of three-body bound states obeying discrete scale invariance when the particles interact resonantly. Because of its universality and peculiarity, the Efimov effect has been the subject of extensive research in chemical, atomic, nuclear and particle physics for decades. In this talk, I will give a pedagogical introduction to the Efimov effect and then discuss our recent studies on its emergence in condensed matter systems [arXiv:1208.6214] and a new universal phenomenon called super Efimov effect [arXiv:1301.4473].

QG Seminar

- Title
- 情報幾何的方法による量子古典対応の解析
- Speaker
- Hiroaki Matsueda (Sendai Natl. Coll. Tech.)
- Date & Time
- Monday, October 28, 2013, 3:00 p.m.
- Place
- QG-Lab Colloquium Room (ES744)

EHQG Seminar

- Title
- Holographic Entanglement Entropy: from quantum many-body systems to emergent spacetime
- Speaker
- Tadashi Takayanagi (YITP, Kyoto Univ.)
- Date & Time
- Tuesday, October 22, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- We will review recent developments on holographic entanglement entropy. Our main goal is to explain an interpretation of spacetime in term s of entanglement structures, based on the tensor network method of quantum many body systems and the properties of excited states.

EHQG Seminar

- Title
- Primordial black hole formations in type-III hilltop inflation models
- Speaker
- Kazunori Kohri (KEK)
- Date & Time
- Tuesday, October 15, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- In some classes of inflation models, large curvature fluctuations are predicted at small scales with satisfying the current observational data reported by Planck satellite experiments and so on. We show that we can check these types of models by using bounds from Primordial Black Hole (PBH), or Ultra Compact Mini Halo formations, or observing the small-scale fluctuations through future experiments of the CMB μ-distortion, 21 cm fluctuations, or gravitational wave. I will briefly review this subject for non-experts in the first 20 minutes of my talk.

EHQG Seminar

- Title
- Precision Cosmology after PLANCK
- Speaker
- Kiyotomo Ichiki (Nagoya Univ.)
- Date & Time
- Tuesday, October 8, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- Precise measurements of the cosmic microwave background (CMB) have provided tight constraints on cosmological models. Here we briefly review the recent results released by the Planck Collaboration, in particular those from the temperature anisotropies and the CMB lensing effect, together with our recent works related to the CMB. We discuss some tensions found between the CMB measurement which mainly target the high-z universe (z=1100), and those in the local universe (z=0), and show how the neutrino physics beyond the standard cosmological model can reconcile those tensions. Future prospects of CMB cosmology are also discussed.

EHQG Seminar

- Title
- Physics of neutron star matter—current status and challenge
- Speaker
- Akira Ohnishi (YITP, Kyoto Univ.)
- Date & Time
- Tuesday, October 1, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- Neutron stars have been serving as laboratories to probe the densest matter in the universe. Recent observation of the two-solar-mass neutron star suggests that strange hadrons do not emerge in dense matter, and may contradict our understanding in hypernuclear physics. Another important suggestion comes from the measurement of neutron star radii. Analyses of photon spectra from X-ray bursts seem to favor very compact size (R∼9 km) of neutron stars, which may rule out most of the proposed nuclear matter EOS. These combinations, (M, R)∼(2 M_sun, 9 km), result in a new view of neutron stars as “almost causality limit objects”. It is a big challenge to achieve consistent understanding of neutron star observations and terrestrial (laboratory) experiments. The grant-in-aid study on innovative area, “Nuclear matter in neutron stars investigated by experiments and astronomical observations” aims at giving insight into neutron star matter equation of state and solving the puzzle. In this seminar, I first give a brief overview on the recent observations of neutron star masses and radii, and their implications. Next, I introduce the plan in the grant-in-aid study on neutron star matter. Finally, I discuss how we can attack the problem of the heavy and compact neutron stars.

Colloquium

- Title
- Gyro Inflation and de Sitter Vacua in the Gauged Maximal Sugra
- Speaker
- Hideo Kodama (KEK)
- Date & Time
- Thursday, September 26, 2013, 2:00 p.m.
- Place
- Science Symposia (ES635)

Special Lecture (for DC)

- Title
- アクシオン宇宙物理
- Speaker
- Hideo Kodama (KEK)
- Date & Time
- Wednesday, September 25–Friday, September 27, 2013
- Place
- Science Symposia (ES635)

EHQG Seminar

- Title
- Dark matter capture in neutron stars
- Speaker
- Motoi Tachibana (Saga Univ.)
- Date & Time
- Tuesday, July 23, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- In this presentation, we would like to discuss some possible effects of dark matter in stellar systems such as compact stars. Specifically, we are interested in the dark matter (DM) capture in neutron stars and its astrophysical implications. With respect to the process, there are 3 important stages, i.e., (1) accretion of DM, (2) thermalization of DM and (3) formation of black-hole and destruction of host neutron stars. In the previous studies, they had simplified neutron star profiles and neglect some interesting possibilities of exotic phases like neutron superfluidity, color superconductivity and such. So we study how the appearance of those phases could affect the scenario of the dark matter capture in neutron stars. Through the studies, one can constrain yet unknown dark matter properties as well as neutron star's.

EHQG-KMI Seminar

- Title
- Quark matter in neutron star
- Speaker
- Mark G. Alford (WUSTL)
- Date & Time
- Tuesday, July 16, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- In this talk I will describe the densest predicted state of matter—color-superconducting quark matter. A color superconductor is very different from an “ordinary” electrical superconductor. It occurs at ultra-high density and has a much richer phase structure because quarks come in many varieties. Quark matter may well exist in the core of neutron stars, and the search for signatures of its presence is currently proceeding. I will give an accessible review of the features of color-superconducting quark matter, and discuss some ideas for finding it in nature.

EHQG Seminar

- Title
- Wilson loop operator in the AdS/CFT correspondence
- Speaker
- Akitsugu Miwa (RIKEN)
- Date & Time
- Tuesday, July 9, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- The AdS/CFT correspondence claims that there are relations between a gravitational theory on the AdS spacetime and a field theory with conformal symmetry. Assuming that the correspondence is really true, we would be able to understand the gravitational theory by studying the dual conformal field theory, or vise verse. However, since the correspondence is still a conjecture, it should be also an important subject to check the correspondence in detail. In this talk, I would like to discuss detailed check of the correspondence by focusing on the Wilson loop operator. I will start with the introduction how the Wilson loop is discussed in the context of the AdS/CFT correspondence. Then I will explain several concrete examples.

EHQG Seminar

- Title
- Entanglement Structures and Holographic Spacetimes of Quantum States
- Speaker
- Hiroaki Matsueda (Sendai Natl. Coll. Tech.)
- Date & Time
- Tuesday, July 2, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- In statistical and condensed matter physics, it has been attracting considerable attention for a decade to apply new types of variational wave functions to the analysis of strongly correlated quantum systems. These functions are constructed so that they satisfy the relevant entanglement-entropy scaling. One promising variational approach is the so-called multi-scale entanglement renormalization ansatz (MERA) for critical quantum systems. Furthermore MERA is recognized to be a discrete version of the AdS/CFT correspondence, and thus interdisciplinary researches are developed. In this talk, I will present basic properties of the entanglement entropy and the variational functions for non-experts. Then, we move to discuss the following two topics: (1) How to define a finite-temperature MERA and whether the MERA is related to the BTZ black hole. (2) Information-geometrical interpretation of the AdS/CFT correspondence.

EHQG Seminar

- Title
- Some Mutant Forms of Quantum Mechanics
- Speaker
- Tatsu Takeuchi (Virginia Tech., Blacksburg)
- Date & Time
- Tuesday, June 25, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- In order to progress our understanding of Quantum Mechanics, we advocate what we call the “geneticist's approach” in which we introduce mutations to the mathematical genotypes of Quantum Mechanics and study how it affects the physical phenotypes of the theory. We show a few examples of such “mutations” and how the predictions of Quantum Mechanics are affected. We argue that in the process, the physical meanings of various mathematical aspects of Quantum Mechanics will be clarified, and further possible directions of evolution will be evinced.

QG Seminar

- Title
- A spherically symmetric solution in Lorentz violating gravitational theory
- Speaker
- Yosuke Misonou (Waseda Univ.)
- Date & Time
- Monday, June 24, 2013, 3:00 p.m.
- Place
- QG-Lab Colloquium Room (ES744)
- Abstract
- Einstein-aether理論は一般相対論に於ける計量場に加え、時間的単位ベクトル場（エーテル場）によって時空を記述する重力理論である。エーテル場の存在は時空のLorentz対称性を破れを伴う。Lorentz対称性は一般相対論が備える最も重要な性質の一つであるが、重力の量子効果を考慮すると紫外発散を除去するための切断により、Lorentz対称性が破れることが示唆されている。Einstein-aether理論はこのような理論のtoy modelとしての側面があり、実際に量子重力理論の有力な候補として注目を集めるHorava-Lifshitz (HL)重力理論との“等価性”が示されている。そのため、Einstein-aether理論に基づいて、その時空構造を議論することは意義を増していると言えよう。本発表ではEinstein-aether理論とHL重力理論が等価である場合として特に球対称解に注目し、その性質を紹介する。

EHQG Seminar

- Title
- Massive gravity and cosmology
- Speaker
- Shinji Mukohyama (KIPMU, Univ. Tokyo)
- Date & Time
- Tuesday, June 18, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- The search for a consistent theory of finite-range gravity is a longstanding problem and well motivated by both theoretical and observational considerations. On the theoretical side, whether there exists such a consistent extension of general relativity by a mass term is a basic question of classical field theory. After Fierz and Pauli's pioneering attempt in 1939, this issue has been attracting a great deal of interest. On the observational side, continuing experimental probes of gravity have revealed new unexpected phenomena at large scales. One of the most profound discovery is the cosmic acceleration, which was found in 1998. The extremely tiny energy-scale associated with the cosmic acceleration hints that gravity might need to be modified in the infrared. The massive gravity is one of the most interesting attempts in this direction. In this talk, after reviewing the history and recent developments of massive gravity, I will describe cosmological solutions and their stability.

EHQG Seminar

- Title
- Study of the relation between confinement and chiral symmetry breaking in a gauge-invariant Dirac-mode expansion method
- Speaker
- Shinya Gongyo (Kyoto Univ.)
- Date & Time
- Tuesday, June 11, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- We develop a gauge-invariant Dirac-mode expansion of the QCD operator such as the Wilson loop and the Polyakov loop. With this method, we investigate the relation between confinement and chiral symmetry breaking in lattice QCD on 6^4 at β=5.6. Even after removing the low-lying Dirac modes, which are responsible to chiral symmetry breaking, we find that the confinement force is almost unchanged. As a result, confinement is not directly related to chiral symmetry breaking through Dirac modes.

EHQG Seminar

- Title
- Hydodynamics in 2+1 and 3+1 dimensions, and Holography
- Speaker
- Rene Meyer (KIPMU, Univ. Tokyo)
- Date & Time
- Tuesday, June 4, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- In this talk I will review recent progress in classifying transport coefficients in 2+1- and 3+1-dimensional charged relativistic fluid dynamics. Motivated by the physics of the quark gluon plasma as well as of certain condensed matter systems, I will in particular focus on new transport effects in the presence of parity violating external field such as magnetic fields or rotation. I will also review holographic realizations of the new transport phenomena.

EHQG Seminar

- Title
- Baryogenesis and Neutrino Oscillation with Light Right-handed Neutrinos
- Speaker
- Hiroyuki Ishida (Tohoku Univ.)
- Date & Time
- Tuesday, May 28, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- We investigate the evaluation of baryon number generation in the νMSM which is the MSM extended by three right-handed neutrinos having their masses lighter than electroweak scale. The generation mechanism is baryogenesis via right-handed neutrino oscillation with lepton number separation. In this work, we derive the kinetic equations for density matrices with exact momentum dependence. We evaluate the amount of generated baryon number more accurately by our kinetic equations. Furthermore, we show the correlation between neutrino observables which are measured by neutrino oscillation experiments and the baryon asymmetry of the universe in the limit of vanishing high energy CP phase. Especially, we found out the difference of dependence on CP phases between neutrino mass hierarchies.

EHQG Seminar

- Title
- Soft graviton effects on Local matter dynamics in de Sitter space
- Speaker
- Hiroyuki Kitamoto (SNU)
- Date & Time
- Tuesday, May 21, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- On the de Sitter background, some modes of gravity contain the scale invariant spectrum which is dominant at the super-horizon scale. It indicates that the corresponding propagator has a logarithmic time dependence which breaks the de Sitter symmetry. We investigate physical effects of soft gravitons on the local dynamics of matter fields at the sub-horizon scale. We show that the infra-red logarithms do not spoil the effective Lorentz invariance in scalar, Dirac and gauge fields. The leading infra-red logarithms can be absorbed by time dependent wave function renormalization factors in these cases. In the interacting field theories with quartic, Yukawa and gauge interactions, we find that the couplings become time dependent with definite scaling exponents. We argue that the relative scaling exponents of the couplings are gauge invariant and physical as we can use the evolution of a coupling as a physical time. Furthermore we clarify how the infra-red effects depend on the change of the quantization scheme: different parametrization of the metric and the matter field redefinition. We found that the parametrization dependence of the metric can be compensated by shifting the background metric. As for the matter field redefinition, the specific choice with the effective Lorentz invariance is singled out by unitarity as the kinetic terms are canonically normalized. References: arXiv:1203.0391, 1204.2876, 1211.3878

QG Seminar

- Title
- ブラックホール地平面上の曲率特異点の解析方法について
- Speaker
- Masashi Kimura (YITP, Kyoto Univ.)
- Date & Time
- Monday, May 20, 2013, 3:00 p.m.
- Place
- QG-Lab Colloquium Room (ES744)
- Abstract
- 曲率特異点の付近では一般相対性理論が破綻すると考えられており、時空上の特異点の存在を知ることは理論の適用範囲を考える上で重要である。通常は、曲率の特異点の存在を示すためには、Ricci scalarやKretschmann invariant R^{abcd}R_{abcd}のような座標不変なscalar量が発散することを見る。しかし、近年、曲率テンソルから作られるscalar量は有限であるにもかかわらず、地平面上に曲率特異点をもつブラックホール解が知られるようになってきた。従来は、これを解析するためには、時空の対称性を用い、特殊な座標系で計算が行われており、簡単な計算で曲率特異点の存在を示すことはできなかった。そこで本発表では、そのような場合にも使えるsimpleな解析方法を提案する。また、この方法を用いると、従来行われていた解析方法では扱えない対称性の低いブラックホール時空に対して曲率特異点の存在を示すことが出来る場合があり、ここでは特にKaluza-Kleinブラックホールの地平面上の特異点について議論を行う。

EHQG Seminar

- Title
- BBN with long-lived CHAMPs
- Speaker
- Masato Yamanaka (Nagoya Univ.)
- Date & Time
- Tuesday, May 14, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- Long-lived charged massive particles (CHAMPs) make an impact on the abundances of light elements in the early universe. The success and failure of the nucleosynthesis is quite sensitive to parameters of the long-lived CHAMPs. I will review exotic reactions generated by the long-lived CHAMPs and the resultant constraints on them. Then I would like to talk about the prediction and the constraint on slepton in SUSY models, which is a one of the candidate of long-lived CHAMPs.

EHQG Seminar

- Title
- Technidilaton Phenomenology for the 125 GeV boson
- Speaker
- Shinya Matsuzaki (Nagoya Univ.)
- Date & Time
- Tuesday, May 7, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- Walking technicolor predicts a light composite scalar, technidilaton, arising as a pseudo Nambu-Goldstone boson for the approximate scale invariance. The technidilaton can be as light as the 125 GeV and its phenomenology is shown to be consistent with the currently reported LHC data on a Higgs-like 125 GeV scalar. I will give a talk about the 125 GeV technidilaton, based on a couple of recent papers.

QG Seminar

- Title
- Analog black holes in AdS/CFT and non-equilibrium steady states
- Speaker
- Shin Nakamura (Nagoya Univ.)
- Date & Time
- Thursday, May 2, 2013, 6:00 p.m.
- Place
- QG-Lab Colloquium Room (ES744)
- Abstract
- I will overview recent papers on application of AdS/CFT correspondence to non-equilibrium physics from the view point of analog black holes on D-branes. In some non-equilibrium steady states, the system can have two different notions of temperature: the temperature of the heat bath and that of the non-equilibrium system attached to the heat bath. The latter can often be referred as “effective temperature.” In the context of the AdS/CFT correspondence, this effective temperature is obtained as a Hawking temperature of an analog black hole on a D-brane, and the things looks to be similar to that of the sonic black hole. I would like to discuss how much the analog black holes in AdS/CFT share the common feature with the conventional sonic black holes, in order to open a new approach to non-equilibrium physics in the language of black holes.

QG Seminar

- Title
- What the axiomatic black hole thermodynamics implies for a correspondence between thermodynamic properties of black holes and ordinary matters.
- Speaker
- Hiromi Saida (Daido Univ.)
- Date & Time
- Wednesday, May 1, 2013, 6:00 p.m.
- Place
- QG-Lab Colloquium Room (ES744)
- Abstract
- We construct an axiomatic formulation of black hole thermodynamics, and then discuss its implication for a correspondence (or a dictionary-like feature of gravity theory) between thermodynamic properties of black holes and ordinary matters: Observing the basic assumptions and axioms of black hole thermodynamics, it is implied that, if a thermodynamic process of black holes does not include the energy flow by gravitational wave, then there seems to exist an equivalent correspondence between the thermodynamic process of black hole and some thermodynamic process of ordinary matters which surrounds the black hole. A key point for the establishment of correspondence between thermodynamic properties of black holes and ordinary matters may be a disappearance of gravitational wave modes in thermodynamic process of black holes. Then, it may also be possible to consider that a steady state (stationary nonequilibrium state) thermodynamic property of ordinary matters can be described by some stationary process of black holes which does not include gravitational wave modes.

EHQG Seminar

- Title
- How can we probe the Copernican principle?
- Speaker
- Chul-Moon Yoo (Nagoya Univ.)
- Date & Time
- Tuesday, April 30, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- In this talk, I would like to give a brief review on non-Copernican universe models and their observational tests. The contents are summarized as follows: Why people have paid attention to non-Copernican models. What kind of models have been ruled out so far. Ultimate observational test of non-Copernican models without dark energy. Non-Copernican inhomogeneity as an systematic error. Current and future works.

EHQG Seminar

- Title
- Supersymmetric dynamics with strongly-coupled ingredients
- Speaker
- Yuji Tachikawa (KIPMU, Univ. Tokyo)
- Date & Time
- Tuesday, April 23, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- When a strongly-coupled QFT has flavor symmetries, we can couple gauge fields to its flavor symmetry currents. We discuss the dynamics of the combined system assuming supersymmetry. As an example, we show that such a combined system can be dual to standard supersymmetric gauge theories. The talk is based on the speaker's collaboration with Gadde, Maruyoshi, Yan and Yonekura.

EHQG Seminar

- Title
- New Aspects of Non-equilibrium Physics from Strings and Gravity
- Speaker
- Shin Nakamura (Nagoya Univ.)
- Date & Time
- Tuesday, April 16, 2013, 5:00 p.m.
- Place
- ES034 Lecture Room
- Abstract
- I am going to talk on my recent works on application of the AdS/CFT correspondence to non-equilibrium statistical physics. The AdS/CFT correspondence maps a strongly-coupled gauge theory to a gravity theory on a curved spacetime. One interesting feature of this map is that the thermal state of the gauge theory is obtained as a black-hole geometry just by solving the Einstein's equation without knowing anything about the thermal distribution in advance. I will claim that this idea can be generalized into the non-equilibrium systems: non-equilibrium states can be obtained by solving the equations of motion in the gravity side, circumventing the difficult problem of finding the non-equilibrium distributions. Then I will go through my recent work on novel non-equilibrium phase transitions of current-driven non-equilibrium steady states that has been discovered by using the idea of AdS/CFT. A possible connection to experiments in the strongly-correlated electron systems will also be discussed. Reference: S. N. PRL109 (2012) 120602.

EHQG Seminar

- Title
- Overview of Electroweak Baryogenesis
- Speaker
- Eibun Senaha (Nagoya Univ.)
- Date & Time
- Tuesday, April 9, 2013, 5:15 p.m.
- Place
- ES034 Lecture Room
- Abstract
- In this talk, electroweak baryogenesis is briefly overviewed including recent topics in this area. First, I will talk about the mechanism of electroweak baryogenesis and apply it to the SM, focusing especially on the baryon number washout criterion. Then I will move on to consider beyond the SM such as the MSSM and the next-to-MSSM and discuss viability of electroweak baryogenesis in those models.