We consider two-component fermions with a zero-range interaction in two and three dimensions and study their transport coefficients—shear viscosity, bulk viscosity, and thermal conductivity—for an arbitrary scattering length. In order to carry out reliable analysis in the strongly correlated regime, such as near the unitarity limit, we employ the quantum virial expansion. The quantum virial expansion is applicable to the high-temperature regime and has been actively used as a non-perturbative method in ultracold-atom physics.
In this talk, I will first review the quantum virial expansion for the resonating fermions and then introduce previous results for the transport coefficients. Next, I will show that the Kubo formula of the shear viscosity and the thermal conductivity evaluated at the lowest order in the quantum virial expansion is reduced to the linearized Boltzmann equation [1]. I will also discuss that the bulk viscosity cannot be calculated from the kinetic theory even in the high-temperature regime [2].

References
[1] KF & Y. Nishida, PRA 103, 053320 (2021).
[2] KF & Y. Nishida, PRA 102, 023310 (2020).

The diffuse flux of supernova neutrinos provides an immediate opportunity to detect stellar core-collapse neutrinos. This signal is spatially isotropic and temporally constant, arising from the combined fluxes of neutrinos emitted from all distant stellar core collapses. It has not been detected yet, but the Super-Kamiokande detector, now upgraded with gadolinium, should detect a few neutrino events every year, providing a new probe of core-collapse neutrinos and the cosmic core-collapse rate. In this talk, I will review predictions of this signal. Inputs from both the theoretical and observational communicates are crucial, and I will cover recent insights gained from both simulations of core collapse and surveys of supernovae. I will close with promising probes in both the discovery and precision phases.

We will have a series of joint-meetings of KEK and NAOJ (National Astronomical Observatory of Japan).
The first on-line meeting is held on Oct. 1, 2021 from 10AM for 2 hours.
There are 6 pedagogical talks of 15 minutes. The slides are written in English, but most talks are given in Japanese. When the COVID19 is settled, we will plan a tour to NAOJ for graduate students.
Please come to the meeting and enjoy the talks of astrophysics.
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[Program]
10:00 – 10:15 津久井 崇史 (国立天文台 総研大5年)：
Takashi Tsukui (NAOJ, Sokendai 5th year) “The measurement of galactic structures in a galaxy more than 12 billion years ago using the gas dynamics”

 

10:20 – 10:35 伊藤 慧 (国立天文台 総研大5年)：
すばる望遠鏡で探る宇宙初期の大規模構造と銀河進化
Kei Ito (NAOJ, Sokendai 5th year
“Large-scale structure and galaxy evolution in the early universe revealed by the Subaru Telescope”

 

10:40 – 10:55 滝脇 知也 (国立天文台 科学研究部助教)：
重力崩壊型超新星爆発で起こるニュートリノ振動
Tomoya Takiwaki (NAOJ, Division of Science, Assistant Professor) “Neutrino oscillation in core-collapse supernovae”

 

11:00 – 11:15 加藤 晶大 (高エネ研 総研大3年):
波長可変赤外レーザーを使ったLiteBIRD衛星の宇宙線ノイズ評価試験
Akihiro Kato (KEK, IPNS, CMB experiment, Sokendai 3rd year), “Characterization of cosmic ray noise of LiteBIRD satellite using a tunable infrared laser”

 

11:20 – 11:35 Rishabh Bajpai (高エネ研 総研大4年):
“Gravitational Wave Detector and Study of Cryogenic Technical Noise in KAGRA”

 

11:40 – 11:55 郡 和範 (高エネ研 理論センター准教授):
天文学と高エネルギー物理学をつなぐ初期宇宙のインフレーション
Kazunori Kohri (KEK, Theory Center, Associate Professor), “Theory of the Inflationary Universe: A unique bridge between astronomy and high-energy physics”

The isocurvature component of the primordial perturbations has been largely ignored ever since CMB experiments established that on large-scales the adiabatic mode dominates. On small scales, however, isocurvature can still play a role. I present a new signal of small-scale isocurvature, the formation of primordial black holes, which I use to derive new model-independent isocurvature constraints. I then discuss the isocurvature we expect in the Standard Model from the evolution of the Higgs field during reheating.

We resolve several puzzles related to the electromagnetic response of topological superconductors in 3+1 dimensions. In particular we show by an analytical calculation that the interface between a topological and normal superconductor does not exhibit any quantum Hall effect as long as time reversal invariance is preserved. We contrast this with the analogous case of a topological insulator to normal insulator interface. The difference is that in the topological insulator the electromagnetic vector potential couples to a vector current in a theory with a Dirac mass, while in the superconductor a pair of Weyl fermions are gapped by Majorana masses and the electromagnetic vector potential couples to their axial currents.

I present some exact non-perturbative results in QCD-like and chiral gauge theories. They are exact when supersymmetric gauge theories are perturbed by anomaly-mediated supersymmetry breaking (AMSB). Thanks to the UV-insensitivity of AMSB, SUSY results can be perturbed with no ambiguities even when applied to composite fields. I analytically derive chiral symmetry breaking in QCD-like theories. Our results for chiral gauge theories do not agree with what had been suggested by tumbling. We suggest alternative schemes of tumbling-like interpretations. We see no evidence that large SUSY breaking leads to phase transitions for the chiral symmetry breaking, perhaps protected by holomorphy.

Highly oscillatory path integrals are common in lattice field theory. They crop up as sign problems and as signal to noise problems and prevent Monte Carlo calculations of both lattice QCD at finite chemical potential and real-time dynamics. A general method for treating highly oscillatory path integrals has emerged in which the domain of integration of the path integral is deformed into a complexified field space. In this talk I will review this method, and I will discuss recent progress in machine learning manifolds for lattice QCD.

Critical slowing down and topological freezing are key obstacles to progress in lattice QCD calculations of hadronic properties causing the cost of ensemble generation to severely diverge in the continuum limit. Recently, a class of machine learning techniques known as flow-based models has been successfully applied to produce exact sampling schemes that can circumvent critical slowing down and/or topological freezing in proof-of-principle applications. This talk summarizes these flow-based MCMC methods, including the incorporation of gauge and translational symmetries. I further discuss progress towards including the contributions of fermions, required for example to include dynamical quark contributions to flow-based sampling for lattice QCD.

We show how Feynman?s path integral for quantum mechanical theories may be defined without a Wick rotation to imaginary time. Instead, we employ analytic continuation (and Cauchy?s theorem) in the complexified space of paths being integrated over. We outline a new existence proof for real time path integrals and describe physical applications, from nonrelativistic quantum mechanics to interference patterns in radio astronomy and caustics in Yang-Mills theories. Our target is gravity: I outline the remaining challenges.

We show how Feynman’s path integral for quantum mechanical theories may be defined without a Wick rotation to imaginary time. Instead, we employ analytic continuation (and Cauchy’s theorem) in the complexified space of paths being integrated over. We outline a new existence proof for real time path integrals and describe physical applications, from nonrelativistic quantum mechanics to interference patterns in radio astronomy and caustics in Yang-Mills theories. Our target is gravity: I outline the remaining challenges.