At the present time, cosmology is presenting us with a wealth of data which can only be explained by invoking new physics operating in the very early universe. I will introduce three paradigms for the evolution of the early universe: inflation, a cosmological bounce, and an emergent scenario. I will argue that in light of arguments from quantum gravity and string theory the inflationary paradigm is severely constrained.
I will then discuss attempts to obtain an emergent cosmology making use of fundamental principles of superstring theory, in particular matrix theory.

I will introduce the notion of target space entanglement. Quantum entanglement is closely related to the structure of spacetime in quantum gravity. For quantum field theories or statistical models, we usually consider the base space entanglement. However, target space instead of base space sometimes directly connects to our spacetime, for example, perturbative string theories. We thus need target space entanglement. To define the target space entanglement, we have to generalize the definition of the conventional entanglement entropy. I will explain this generalization and apply it to the first quantized particles, in particular, fermions.

Recently, the new phase of the two-flavor color superconductor was proposed in connection with the recent discussion on the equation of state of neutron stars [1]. In this talk, I will show the classification of the topological vortices in this phase. We found that the most stable vortices are what we call the “non-Abelian Alice strings” [2]. They are superfluid vortices carrying 1/3 quantized circulation and color magnetic fluxes. I will discuss in some details about their properties in comparison to the well-established CFL vortices in three-flavor symmetric setup, by putting some emphasis on their peculiarity: the non-Abelian generalization of the Alice property. I will also discuss the confinement of the vortices as well as how the vortices in the quark phase are connected to those in the hadronic phase [3].

References:
[1] Y. Fujimoto, K. Fukushima, W. Weise, Phys. Rev. D 101, 094009 (2020), arXiv:1908.09360 [hep-ph].
[2] Y. Fujimoto, M. Nitta, Phys. Rev. D 103, 054002 (2021), arXiv:2011.09947 [hep-ph]; JHEP 09 (2021) 192, arXiv:2103.15185 [hep-ph].
[3] Y. Fujimoto, M. Nitta, Phys. Rev. D 103, 114003 (2021), arXiv:2102.12928 [hep-ph].

We will discuss a method to calculate the rate of false vacuum decay induced by a black hole. The method uses complex tunnelling solutions and consistently takes into account the structure of quantum vacuum associated to the black hole. We will illustrate the technique on a two- dimensional toy model of a scalar field with inverted Liouville potential in an external background of a dilaton black hole. Using this model, we will compute the exponential suppression of tunnelling from the Boulware, Hartle-Hawking and Unruh vacuum states and show that they are parametrically different. Finally, we will discuss how our results are generalised to the realistic case of black holes in four dimensions.

In this talk I will first review a long-standing discrepancy between the neutron lifetime as measured in beam and in bottle experiments. If this discrepancy is not due to a systematic error, it may be due to novel mechanisms for neutron transmutation into new, as yet unknown elementary particles. These particles would be electrically neutral, or so-called “dark”. We will explain several scenarios for the possibility of neutron transmutation into dark particles. For example, in one interesting scenario the products of the neutron transmutation include a monochromatic photon with energy in the range 0.782 MeV?1.664 MeV and this is predicted to occur in 1% of all neutron decays. We will describe recent theoretical developments as well as ongoing and planned experiments looking directly to establish or rule out the “dark decay” hypothesis.

機械振動子は外力に対するセンサーとして古くから利用されてきた。近年では、振動子とレーザー光を光共振器で結合させることで、極めて高感度な振動子の変位計測（つまり、力計測）が実現可能となってきている。特に、振り子は重力ポテンシャルの影響によって極めて低散逸な振動子となるため、揺動散逸定理から、熱的な揺動力の小さな良質なセンサーとして応用できることが知られている。
２０１５年に達成された重力波の直接検出は、振り子振動が極めて低散逸なために実現したと言える。
センサーの性能を究極に向上すれば、振動子の量子揺らぎ程度の空間分解能でさえ、原理的には到達可能となる。しかし、振動子の位置の量子揺らぎの大きさは、振動子の質量が大きくなればなるほど小さくなるため、その実現は困難となる。本講演では、質量ミリグラムスケールの極めて巨視的な振り子の重心振動の量子計測と制御の原理検証について紹介する。
特に、振動子の重心振動と回転振動の光学トラップ、精密変位計測の実現、低散逸振り子の開発、振動子の量子状態推定について説明する。これらの基盤技術の融合により、近い将来、2つの巨視的な振り子の間の量子エンタングルメント状態が生成可能となるだろう。このような技術開発の果てに、量子制御された物体が生じる重力の性質を検証するといった新たな研究領域が創成する可能性がある。
また、外力センサーとして応用すれば、超軽量ダークマター・相対論的な重力の探索、重力定数の精密測定といった新たな応用につながることが期待される。　

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.
———————-

[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.