Tomo Takahashi, Saga University
Aspects of non-minimal inflation
Meeting room 1, Kenkyu honkan 1F
We discuss models of inflation where the inflaton is non-minimally coupled to gravity in some general setting, focusing on their predictions on inflationary observables such as the spectral index and tensor-to-scalar ratio. We consider both metric and Palatini formalisms of gravity and argue that how some inflation models can be alleviated by introducing a non-minimal coupling to gravity. The issues of distinguishing variants of such models are also discussed.
Andrew Lytle, INFN, Sezione di Roma Tor Vergata
b->c semileptonic decays and phenomenology
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
There are at the moment a number of long-standing discrepancies between observables in b->c semileptonic decays and their Standard Model predictions. In addition there is the long-standing tension between inclusive and exclusive determinations of Vcb, the latter being obtained from these same decays. Here I will discuss the state-of-the-art lattice simulations addressing these issues. After reviewing the status of B->D(*) form factors I will discuss in more detail new results from HPQCD that treat the ‘b’ quark fully relativistically.
Keisuke Yanagi, Department of Physics, University of Tokyo
Dark Matter Heating vs. Rotochemical Heating in Old Neutron Stars
Seminar room, Kenkyu honkan 3F
Dark matter (DM) particles in the Universe accumulate in neutron stars (NSs) through their interactions with ordinary matter. It has been known that their annihilation inside the NS core causes late-time heating, with which the surface temperature becomes a constant value of Ts≃(2−3)×10^3 K for the NS age t≳10^{6−7} years. This conclusion is, however, drawn based on the assumption that the beta equilibrium is maintained in NSs throughout their life, which turns out to be invalid for rotating pulsars. The slowdown in the pulsar rotation drives the NS matter out of beta equilibrium, and the resultant imbalance in chemical potentials induces late-time heating, dubbed as rotochemical heating. This effect can heat a NS up to Ts≃10^6 K for t≃10^{6−7} years. In fact, recent observations found several old NSs whose surface temperature is much higher than the prediction of the standard cooling scenario and is consistent with the rotochemical heating. Motivated by these observations, in this letter, we reevaluate the significance of the DM heating in NSs, including the effect of the rotochemical heating. We then show that the signature of DM heating can still be detected in old ordinary pulsars, while it is concealed by the rotochemical heating for old millisecond pulsars. To confirm the evidence for the DM heating, however, it is necessary to improve our knowledge on nucleon pairing gaps as well as to evaluate the initial period of the pulsars accurately. In any cases, a discovery of a very cold NS can give a robust constraint on the DM heating, and thus on DM models. To demonstrate this, as an example, we also discuss the case that the DM is the neutral component of an electroweak multiplet, and show that an observation of a NS with Ts≲10^3 K imposes a stringent constraint on such a DM candidate.
Kazunobu Maruyoshi, Seikei University
Landscape of Superconformal Field Theories in 4d
Meeting room 1, Kenkyu honkan 1F
Abstract: Classification of superconformal field theories (SCFTs) is an important question in theoretical physics. We would like to (partially) answer this question focusing on SCFTs in four dimensions realized in the fixed points of the renormalization group flow induced by certain deformations of “known” SCFTs. The deformations include all possible relevant deformations and F-term couplings to gauge-singlet chiral multiplets. By “known” we mean we know the superconformal index in enough higher order. With this knowledge our deformation program is well defined and produces various fixed points. As simple examples, we see the deformations of the N=2 Argyres-Douglas theory, and of N=1 supersymmetric SU(2) gauge theory coupled to an adjoint and two fundamental chiral multiplets. In particular, from the latter theory, we find 34 fixed points, which cover all the known (low central charge) SCFTs and the interesting unknown ones, and 36 candidate fixed points possessing unphysical operators, including one with (a, c)=(0.20, 0.22), that need further investigation.
Mark Barton (NAOJ）
Design and status of KAGRA
Seminar room, Kenkyu honkan 3F
KAGRA is a 3-km laser-interferometric gravitational-wave detector under construction in Japan to form part of a network with other advanced detectors such as LIGO and Virgo. Innovative features include underground construction for lower seismic noise and cryogenic operation for lower thermal noise. Construction of the bKAGRA phase is essentially complete, and commissioning is underway, with the goal of participating in the LIGO/Virgo O3 observing run towards the end of 2019. The design and status of the detector are described.
Yu Sang, Institute of Theoretical Physics, Chinese Academy of Sciences
Stochastic gravitational wave background from reheating
Seminar room, Kenkyu honkan 3F
In preheating stage after inflation, fluctuations of inflaton field may be enhanced exponentially by parametric resonance. The large and time dependent density inhomogeneity will produce stochastic gravitational wave background. We use lattice simulation to study the non-perturbative evolution of the inflaton field and the production of gravitational waves. We focus on axion monodromy inflation model and find that significant single-peak stochastic gravitational wave backgrounds are generated during preheating.
Junsei Tokuda, Department of Physics, Kyoto University
IR obstruction to Lorentz invariant UV completion
Seminar room, Kenkyu honkan 3F Recently, it has been recognized that low energy effective field theory must satisfy an infinite number of positivity bounds when UV completion is local, analytic, unitary, and Lorentz invariant. In this talk, I will firstly review the derivation of positivity bounds and their importance. Then, I will introduce our recent work in which we show that the locality assumption is not necessary to derive some of positivity bounds obtained in the literature. Such bounds may provide IR obstructions to analytic, unitary, and Lorentz invariant UV completion.
Recently, it has been recognized that low energy effective field theory must satisfy an infinite number of positivity bounds when UV completion is local, analytic, unitary, and Lorentz invariant. In this talk, I will firstly review the derivation of positivity bounds and their importance. Then, I will introduce our recent work in which we show that the locality assumption is not necessary to derive some of positivity bounds obtained in the literature. Such bounds may provide IR obstructions to analytic, unitary, and Lorentz invariant UV completion.
References :
Junsei Tokuda, arXiv:1902.10039
全卓樹, 高知工科大学
世論力学：数理的な政治社会学の試み
Seminar room, Kenkyu honkan 3F
多数決は生物社会の集団的意思決定における遍在的な原理であり、人類の民主主義社会もその一例である。民主主義な多数決には、その単純な見かけとは裏腹ないくつかの「逆理」が知られていて、少数ながら強い影響力を振るう利益団体の存在、冷笑的反対派が既存優越派の補完勢力となる事象、などがいたるところで観察されるのである。われわれは社会集団における多数派の形成を、スピン・モデルに範をとって数理物理学の枠組みに載せてモデル化した理論、「世論力学」を発展させた。このモデルが「多数決民主主義の実態」を、諸逆理を含めて、よく記述している様子を解説する。
Hidenori Fukaya, Osaka University
Atiyah-Patodi-Singer index theorem and domain-wall fermions
Meeting Room 1, Kenkyu honkan 1F, slides (kek.jp only)
The Atiyah-Patodi-Singer index theorem describes the bulk-edge correspondence of symmetry protected topological insulators. The mathematical set-up for this theorem is, however, not directly related to the physical fermion system, as it imposes on the fermion fields a non-local boundary condition known as the “APS boundary condition” by hand, which is unlikely to be realized in the materials. In 2017, we showed that the same integer as the APS index can be obtained from the eta-invariant of the domain-wall Dirac operator. In this work, we invite three mathematicians to our group and prove that this correspondence is not a coincidence but generally true.
Naoki Yamamoto, Department of Physics, Keio University
Chiral Soliton Lattice in QCD
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
