セミナー 2014年

Yuki Yokokura, Yukawa Inst., Kyoto Univ.

Non-equilibrium thermodynamics of gravitational screens

Seminar room, Kenkyu honkan 3F
We study the Einstein gravity equations projected on a timelike surface, which represents the time evolution of what we call a gravitational screen. We show that such a screen possesses a surface tension and an internal energy, and that the Einstein equations reduce to the thermodynamic equations of a viscous bubble. We also provide a complete dictionary between gravitational and thermodynamical variables. In the non-viscous cases there are three thermodynamic equations which characterize a bubble dynamics: These are the first law, the Marangoni flow equation and the Young-Laplace equation. In all three equations the surface tension plays a central role: In the first law it appears as a work term per unit area, in the Marangoni flow its gradient drives a force, and in the Young-Laplace equation it contributes to a pressure proportional to the surface curvature. The gra vity equations appear as a natural generalization of these bubble equations when the bubble itself is viscous and dynamical. In particular, it shows that the mechanism of entropy production for the viscous bubble is mapped onto the production of gravitational waves. We also review the relationship between surface tension and temperature, and discuss the usual black-hole thermodynamics from this point of view. (This talk is based on [arXiv:1405.4881].)

Yu Nakayama, Kavli IPMU, Caltech

Understanding phase transitions and critical phenomena from conformal bootstrap

Meeting room 1, Kenkyu honkan 1F
Conformal bootstrap has become an indispensable tool to understand the non-perturbative aspects of renormalization group fixed points in any space-time dimension. The recent “solution” of the d=3 critical Ising model is just one example.
In this talk, I would like to discuss the real applications of conformal bootstrap to attack the long-standing controversies on the phase transitions and critical phenomena of the frustrated spin systems in non-collinear order and the finite temperature QCD chiral transition by determining the conformal windows of O(n)xO(m) CFTs in d=3 dimensions.
The talk is based on our recent paper arXiv:1404.0489 in collaboration with Tomoki Ohtsuki.

Kazuki Sakurai, King's College

ATOM/Fastlim: Recasting LHC constraints on new physics models

Meeting room 1, Kenkyu honkan 1F
The results of ATLAS and CMS beyond the Standard Model searches are very useful to constrain various new physics modes, yet they are originally designed to search for a particular model. Recasting existing analyses on to an arbitrary model involves various subtleties and one has to simulate detector responses and selection cuts as realistic as possible. For this task, we developed two programs: ATOM (Automated Testing Of Models) and Fastlim. ATOM takes event files as inputs and calculates the efficiencies of various analyses automatically, which can be used to calculate an exclusion p-value for an given model. Fastlim, on the other hand, takes spectrum files as inputs and immediately calculates an exclusion p-value using pre-calculated efficiencies of various simplified topologies. In this talk, I review the recent development of the attempt of recasting ATLAS and CMS searches on to general new physics models. I also discuss the methodology used and present performances of ATOM and Fastlim.

Masahide Yamaguchi, Tokyo Institute of Technology

Non-Gaussianities of primordial perturbations and tensor sound speed

Meeting room 1, Kenkyu honkan 1F
We investigate the relation between the non-Gaussianities of the primordial perturbations and the sound speed of the tensor perturbations, that is, the propagation speed of the gravitational waves. We find that the sound speed of the tensor perturbations is directly related not to the auto-bispectrum of the tensor perturbations but to the cross-bispectrum of the primordial perturbations, especially, the scalar-tensor-tensor bispectrum. This result is in sharp contrast with the case of the scalar (curvature) perturbations, where their reduced sound speed enhances their auto-bispectrum. Our findings indicate that the scalar-tensor-tensor bispectrum can be a powerful tool to probe the sound speed of the tensor perturbations.

Keisuke Harigaya, Kavli IPMU

Natural inflation with effective large decay constant by hierarchical charge

Meeting room 1, Kenkyu honkan 1F
Natural inflation is a large field model, which is favored from the view point of the initial condition problem.The inflaton can be understood as a Nambu Goldstone boson associated with a spontaneous breaking of an U(1) symmetry. The inflaton potential can be understood as an explicite breaking of the U(1) symmetry to a discrete one. Since the decay constant of the inflaton must be larger than the Planck scale for a successful slow-roll inflation, it is not clear whether natural inflation model can be treated by four dimensional field theory, which has a cut off at the Planck scale. In this talk, I show that the large decay constant can be obtained from a field theory with all the scale below the Planck scale, by considering hierarchical U(1) charges.

Masato Taki, RIKEN Nishina Center

Seiberg Duality, 5d SCFTs and Nekrasov Partition Functions

Meeting room 1, Kenkyu honkan 1F
We propose a duality between various Type IIB 5-brane web configurations, and this conjecture implies an equality between the corresponding 5d Nekrasov partition functions (i.e. refined topological string partition functions) that are associated with local del Pezzo surfaces. It is known that M-theory compactified on a local Calabi-Yau 3-fold leads to a 5d superconformal field theory (SCFT), and this system is dual to a Type IIB 5-brane web system. One can expect that the “Picard-Lefschetz transformation” of these 3-folds implies the duality between these brane setups and the resulting 5d SCFTs. We then find that many different Type IIB 5-brane webs describe the same 5d SCFT that was found by N.Seiberg. We check this duality by comparing the Nekrasov partition functions of these 5-brane web configurations.

佐々木寿彦, 理化学研究所


Meeting room 1, Kenkyu honkan 1F
量子力学では相補的な物理量同士は同時に決定できない。Einsten-Podolsky-Rosen や Kochen–Specker の議論では、このことと仮想的な実験の切り替えを考えあわせることにより、量子力学における実在性の非自明な姿を炙りだした。この様な議論には実用上の応用法があり、実際の通信においても仮想的な実験を考えることで、通信路の性質を強く特徴付けることができる場合がある。本発表では、この様な議論の現状を紹介したい。

Kai Schmitz, Kavli IPMU

Hybrid or Chaotic? The Current Status of Inflation from a Subjective Perspective

Meeting room 1. Kenkyu honkan 1F
Precise measurements of the B-mode polarization of the cosmic microwavebackground are crucial for our understanding of cosmic inflation. If upcomingobservations should confirm the large tensor signal recently reported by theBICEP2 collaboration, inflation may have simply been driven by a simplemonomial potential as employed in models of chaotic inflation. If, on the otherhand, the BICEP2 signal should disappear once the dust (polarization issue) has(been) settled, attention might shift again towards small-field models of inflationbecause of their attractive properties on the particle physics side. In this talk, Iwill discuss both scenarios for the possible fate of our understanding of cosmicinflation and present recent results on explicit models that either predict a verylarge or a very small tensor-to-scalar ratio. First, I will illustrate how stronglyinteracting supersymmetric gauge theories can give rise to inflationary dynamicsthat mimic those of chaotic inflation, cf. 1403.4536 [hep-ph]; then I will revisitsupersymmetric F-term hybrid inflation and demonstrate how a notoriouslyoverlooked feature of this model can render it consistent with all observations(except for BICEP2) after all, cf. 1404.1832 [hep-ph]).

Shun Saito, Kavli IPMU

Neutrino mass constraint from robust cosmological signals in the BOSS DR11 galaxy clustering

Meeting room 1, Kenkyu Honkan 1F
In this talk I will first give a brief highlight of ~1% measurement of the cosmological distance via Baryon Acoustic Oscillation (BAO) and ~10% measurement of the growth of large-scale structure via Redshift-Space Distortion (RSD) as fairly robust cosmological signals at z~0.5 from the updated data-relrease 11 (DR11) of Baryon Oscillation Spectroscopic Survey (BOSS). BOSS is part of Sloan Digital Sky Survey III (SDSS-III), and a gigantic cosmological survey aiming at mapping 1.5 million luminous galaxies and 200,000 quasars. BOSS DR11 contains almost million galaxies over 8,500 deg^2 which is currently the best 3-dimensional map of galaxies in the universe. I will describe how to efficiently measure BAO and RSD from such a huge dataset, and discuss how useful BAO and RSD are. In particular, I will focus on the neutrino mass constraint using BOSS BAO and RSD, and discuss how the neutrino mass can resolve discrepancies among cosmological datasets at early and at late time.
Refs. http://arxiv.org/abs/1312.4611 , http://arxiv.org/abs/1403.4599

Xiang Liu, School of Physical Science and Technology, Lanzhou University

Charged charmonium-like structures and the initial single chiral particle emission mechanism

Seminar Room, Kenkyu Honkan 3F
In this talk, I will introduce how the ISPE mechanism is introduced to explain the charged bottomonium-like states Zb(10610) and Zb(10650). Later, I will illustrate the relation between the prediction of charged charmonium-like structures and the observed charged charmonium-like states Zc(3900) and Zc(4025). By the ISChE mechanism, more abundant phenomena of charged charmonium-like structures were predicted, which will be introduced in this talk.

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