Hiroyuki Kitamoto, Kyoto U.
Generalization of Stochastic approach for Infrared effects
Meeting Room 1, Kenkyu Honkan 1F
We extend investigations of infrared dynamics in accelerating universes. In the presence of massless and minimally coupled scalar fields, physical quantities may acquire growing time dependences through quantum fluctuations at super-horizon scales. From a semiclassical viewpoint, it was proposed that these infrared effects can be described by a Langevin equation. In de Sitter space, the stochastic approach has been proved to be equivalent to the leading power resummation of the growing time dependences. In this study, we make the resummation derivation of the Langevin equation in a general accelerating universe. The resulting Langevin equation contains a white noise term and the coefficient of each term is modified by the slow-roll parameter. Furthermore we show that the semiclassical description of the scalar fields leads to the same stochastic equation as far as we adopt an appropriate time coordinate.
The above investigations are performed in models whose nonlinear terms are given by potentials. Therefore the stochastic approach should be extended in another direction, i.e. in models with derivative interactions. If time allows, I also talk about this direction of generalization.
Yuta Hamada, Kyoto U.
Reheating-era leptogenesis
Meeting Room 1, Kenkyu Honkan 1F
We propose a novel leptogenesis scenario at the reheating era. Our setup is minimal in the sense that, in addition to the standard model Lagrangian, we only consider an inflaton and higher dimensional operators. The lepton number asymmetry is produced not by the decay of a heavy particle, but by the scattering between the standard model particles. After the decay of an inflaton, the model is described within the standard model with higher dimensional operators. The Sakharov’s three conditions are satisfied by the following way. The violation of the lepton number is realized by the dimension-5 operator. The complex phase comes from the dimension-6 four lepton operator. The universe is out of equilibrium before the reheating is completed. It is found that the successful baryogenesis is realized for the wide range of parameters, the inflaton mass and reheating temperature, depending on the cutoff scale. Since we only rely on the effective Lagrangian, our scenario can be applicable to various mechanisms to generate neutrino Majorana masses.
Shoichi Kawamoto, Chung Yuan Christian U
Size scaling of self gravitating polymers and strings
Meeting room 3, Kenkyu honkan 1F
We study a statistical ensemble of a single polymer with self gravitational interaction. This is a model of a gravitating string — the precursor of a black hole. We analyze averaged sizes by mean field approximations with an effective Hamiltonian a la Edwards with Newtonian potential as well as a contact repulsive interaction. We find that there exists a certain scaling region where the attractive and the repulsive forces balance out. The repulsive interaction pushes the critical gravitational coupling to a larger value, at which the size of a polymer becomes comparable to its Schwarzschild radius, and as a result the size of the corresponding black hole increases considerably. This talk is based on the joint work with T. Matsuo (NIT, Anan College), Prog. Theor. Exp. Phys. (2015) 123B02.
Chen-Pin Yeh, National Dong-Hwa U
Holographic Description of Negative Energy in Squeezed States
Meeting room 3, Kenkyu honkan 1F
Using the AdS/CFT duality, we study the properties of negative energy in strongly coupled field theories with the general dynamical scaling. The gravitational wave propagates in the Lifshitz background is dual to the squeezed state in the quantum critical theories. The energy density to leading order in the squeezed parameters can oscillate between negative and positive values with the sub-leading term which is always positive and time independent. We showed that this is consistent with the quantum interest conjecture and satisfies the average null energy condition. And we found a constrain on the duration of negative energy.
Yuichiro Tada, IPMU
Stochastic-delta N formalism and massive primordial black holes in hybrid inflation
Meeting Room 1, Kenkyu Honkan 1F
As a long-studied astrophysical open question, it is known that almost all galaxies possess one or a few supermassive black holes (SMBHs) whose masses reach 10^{6—9.5} M_\odot in their centers. Such SMBHs have been found even at high redshifts as z~6–7 but their production mechanism is still unknown. One possible solution is the primordial black hole (PBH), which is theoretically suggested to be produced by a gravitational collapse of an overdense Hubble patch in the radiation dominant era. It has been proposed that sufficient massive PBHs can be the seeds of SMBHs. In our recent papers, we studied the possibility whether such massive PBHs can be produced in well-know hybrid inflation which is the inflation model ended by a second order phase transition. While that phase transition is roughly estimated to make large curvature perturbations enough to produce PBHs, there have been no quantitatively complete works yet because of the non-perturbative behavior around the critical point. Therefore, we proposed a non-perturbative algorithm to calculate the curvature perturbations at first, combining the stochastic and delta N formalism. Then we performed a wide numerical parameter search to find that PBHs are rather overproduced with the parameters which can make PBHs massive enough. In other words, we showed that massive PBHs cannot be produced with the proper abundance in hybrid inflation, without any specific assumption of the types of hybrid inflation.
Nobuhito Maru, Osaka City University
Predictions of Higgs mass and Weinberg angle in 6D gauge-Higgs unification
Meeting Room 1, Kenkyu Honkan 1F We address a question whether there exists a model of gauge-Higgs unification in 6-dimensional space-time, which successfully predicts the Weinberg angle and the mass ratios between Higgs boson and weak gauge bosons.
We address a question whether there exists a model of gauge-Higgs unification in 6-dimensional space-time, which successfully predicts the Weinberg angle and the mass ratios between Higgs boson and weak gauge bosons.
First, we give a general argument on the condition to get a realistic prediction of the Weinberg angle, and find that triplet and sextet representations of the minimal SU(3) gauge group lead to the realistic prediction.
We notice that in the models with one Higgs doublet, the predicted Higgs mass is always twice the W-boson mass at the leading order.
However, in models with two Higgs doublets, Higgs mass can be smaller than twice the W-boson mass.
Nilakash Sorokhaibam, TIFR
2D Critical Quench, Thermalization and Non-Universality
Meeting room 3, Kenkyu honkan 1F
I will talk about about my last two papers. We studied the long time behaviour of local observables following a quantum quench in 1+1 dimensional conformal field theories possessing additional conserved charges besides the energy. We showed exponential approach to equilibrium of finite sub-interval characterized by a temperature and chemical potentials defined in terms of the quenched state. We compute the exact wavefunction that results from a quantum quench to a vanishing mass, in a large class of examples The resulting wavefunction is of a generalized Calabrese-Cardy form i.e., conformal boundary state deformed by an infinite number of charges. Special squeezed states with small chemical potentials show equilibration to a Generalized Gibbs Ensemble(GGE). By contrast, with general pre-quench states, including the ground state, the chemical potentials are not small; exact correlators in these cases, although equilibrating at long times, do not generically have a simple thermal or GGE form even at large distances. The main lesson is that in 2D critical quench, long time and large distance physics can be sensitive to perturbations by high dimension operators,contrasting general Wilsonian lore.
Bum-Hoon Lee, CQUeST, Sogang U., Korea
Fubini Instantons in curved spacetime
Meeting Room 3, Kenkyu Honkan 1F
TBA
Masato Nozawa, University of Milan
Supersymmetry of (Euclidean) Plebanski-Demianski solution
Meeting Room 3, Kenkyu Honkan 1F,
The Plebanski-Demianski (PD) solution has played a central role in the development of black-hole physics in general relativity since it describes the most general Petrov D metric in Einstein-Maxwell-Lambda system. Recently, Houri and Yasui have found a new king of nondegenerate rank-2 Killing-Yano (KY) tensor in the self-dual Euclidean PD metric. I will discuss in detail how this makes consistent with the theorem by Houri-Oota-Yasui, according to which the local metric admitting a non-degenerate rank 2 KY tensor must fall into the Carter family. It turns out that this is closely related to the fact that the self-dual PD solution preserves half of supersymmetry, whereas the non-self-dual solution admits only one quarter of supersymmetry. I will also explore the underlying mathematical structure of Euclidean PD solution, such as conformal ambi-Kahler structure and new type of Einstein-Weyl space.
Kei Yagyu, University of Southampton
Synergy between direct and indirect searches of non-minimal Higgs sectors
Meeting Room 3, Kenkyu Honkan 1F I would like to review on recent my phenomenological research of non-minimal Higgs sectors especially focusing on two Higgs doublet models.
