In this seminar, I will talk about how temperature observations of neutron stars provide a unique window to explore physics beyond the Standard Model of particle physics. Neutron stars, with their extreme environments, serve as natural laboratories for testing the limits of our physical understanding. The standard cooling theory, which accounts for the cooling of isolated neutron stars through neutrino and electromagnetic radiation, generally aligns with observational data. However, the presence of hypothetical particles such as axions and dark matter, predicted by theories that extend the Standard Model, could alter this cooling behavior. Axions, for example, increase cooling rates, while dark matter interactions could lead to additional heating. By comparing revised theoretical predictions with observed temperature evolution, we might explore signs of these elusive particles. This talk is based on the following papers: arXiv:2309.02633, 2308.16066, 2204.
02413, 2204.02238, 2008.03924, 1905.02991, 1904.04667, 1806.07151.

Particulate dark matter (DM), completely isolated from the Standard Model particle sector, can be produced in the early Universe from primordial black hole (PBH) evaporation. However, big bang nucleosynthesis (BBN) observations put an upper bound on the initial mass of PBH requiring the PBH to evaporate completely before the advent of BBN. DM particles in the mass range ∼(1–10^9)GeV cannot explain the observed relic abundance for an early matter dominated universe due to this BBN constraint. However, this assumes the presence of only one monochromatic PBH mass distribution in the early Universe. In this talk, we will explore the simple possibility of achieving the observed relic with DM masses from the above mentioned range for an early matter dominated era with two monochromatic evaporating PBH mass distributions and demonstrate that the fermionic DM masses consistent with BBN change slightly.

t is known that the 2+1d single Majorana fermion theory has an anomaly of the reflection, which is canceled out when 16 copies of the theory are combined. Therefore, it is expected that the reflection symmetric boundary condition is impossible for one Majorana fermion, but possible for 16 Majorana fermions. In this study, we consider a reflection symmetric boundary condition that varies at a single point, and find that there is a problem with one Majorana fermion. The problem is the absence of a corresponding outgoing wave to a specific incoming wave into the boundary, which leads to the non-conservation of the energy. For 16 Majorana fermions, it is possible to connect every incoming wave to an outgoing wave without breaking the reflection symmetry. In addition, we discuss the connection with the fermion-monopole scattering in 3+1 dimensions. This talk is based on arXiv:2306.10845.

https://www-conf.kek.jp/kincha/
QUPでは、様々なスキルを持つ研究者が、新しい発想で、素粒子・宇宙の真の姿を見る「新しい眼」の開発に取り組んでいます。これまでの素粒子・宇宙プロジェクトでは使われていないような、量子効果を取り入れた全く新しいタイプの検出器のアイデアも生まれてきています。これらの開発は、長い目で社会にも役立つと期待されます。本講演では、QUPが設立されてからおよそ2年間の成果と、これからの展望を紹介します。

The Belle II collaboration recently announced that they observed the B → Kνν decay process for the first time. This dineutrino mode of B+ → K+ν¯ν has been theoretically identified as a very clean channel. However, their result encounters a 2.8σ deviation from the Standard Model (SM) calculation. On the other hand, last year, Fermilab released new data on muon (g − 2) away from the SM expectation with 5σ. In this talk, we will study the simplest UV-complete U(1)Lµ−Lτ -charged Dark Matter (DM) model.
Thanks to the existence of dark Higgs boson and dark photon in this model, we can explain the observed relic density of DM and resolve the anomalous results reported by both Belle II and Fermilab experiments simultaneously without any modification of the thermal history of the Universe.

We describe how the general mechanism of partial deconfinement applies to large-N QCD and the partially deconfined phase inevitably appears between completely-confined and completely-deconfined phases. Furthermore, we propose how the partial deconfinement can be observed in the real-world QCD with the SU(3) gauge group. For this purpose, we employ lattice configurations obtained by the WHOT-QCD collaboration and examine our proposal numerically. In the discussion, the Polyakov loop plays a crucial role in characterizing the phases, without relying on center symmetry, and hence, we clarify the meaning of the Polyakov loop in QCD at large N and finite N. As a nontrivial test for our proposal, we also investigate the relation between partial deconfinement and instanton condensation and confirm the consistency with the lattice data. As a nontrivial application, we show that computation of the two-point correlator of Polyakov loops in the confined phase reduces to the problem of random walk on group manifold. As a consequence, linear confinement potential with approximate Casimir scaling follows immediately.

Recent inference results of the sound velocity in the cores of neutron stars are summarized. Implications for the equation of state and the phase structure of highly compressed baryonic matter are discussed. In view of the strong constraints imposed by the heaviest known pulsars, the equation of state must be very stiff in order to ensure the stability of these extreme objects. This required stiffness limits the possible appearance of phase transitions in neutron star cores. For example, a Bayes factor analysis quantifies strong evidence for squared sound velocities c_s^2 > 0.1 in the cores of 2.1 solar-mass and lighter neutron stars. Only weak first-order phase transitions with a small phase coexistence density range \Delta\rho/\rho < 0.2 (at the 68\% level) in a Maxwell construction still turn out to be possible within neutron stars. The central baryon densities in even the heaviest neutron stars do not exceed five times the density of normal nuclear matter. In view of these data-based constraints, much discussed issues such as the quest for a phase transition towards restored chiral symmetry and the active degrees of freedom in cold and dense baryonic matter, are reexamined.

Preserving the symmetries of massless fermions is a well-known challenge in lattice field theory. I’ll discuss symmetry-preserving lattice regularizations of 2d QED with one and two flavors of Dirac fermions, as well as the `3450′ chiral gauge theory. The construction leverages bosonization and recently-proposed modifications of Villain-type lattice actions. The internal global symmetries act just as locally on the lattice as they do in the continuum, the anomalies are reproduced at finite lattice spacing, and in each case we’ve found a sign-problem-free dual formulation.

https://www-conf.kek.jp/kincha/
海底鉱物資源には，長い地球の歴史で，海におけるグローバルな物質循環の中で，あるタイミングで，その場所に起きた元素濃集と言える。そこには，理由があり，その理由を科学的に明らかにすることは，海洋の物質循環を明らかするのみでなく，海底資源開発のための三要素：探査，採鉱，製錬にも大きく貢献する。本講演では，海底資源研究の最前線とその開発への応用とともに開発に向けた課題について，実際の鉱物資源をご覧に入れながら説明する。　　　　

Axial gauge has been used in many perturbative calculations. However, it sometimes leads to puzzling results. In this talk, I will discuss a specific example in the context of heavy quark and quarkonium transport coefficients, where naive application of temporal axial gauge leads to an incorrect result. Then I will discuss the origin of the problem from both perturbative and nonperturbative aspects. Finally I will summarize the applicability condition of axial gauge and give a few examples.