Sterile neutrino is a decaying dark matter candidate which can be produced non-thermally in the early Universe. Gauged B-L symmetric extension of the standard model naturally accommodates such a sterile neutrino dark matter, and also provides new mediators, B-L gauge boson and symmetry breaking scalar boson. Viable ranges of the dark matter mass and coupling have been studied in this mode. In this talk, we reexamine the freeze-in production of the sterile neutrino dark matter in gauged B-L model. Longitudinal mode contributions in scattering processes as well as inverse decays of the B-L gauge boson and scalar boson are taken into account in our analyses. We will discuss the contributions from these for different mass spectra of the dark matter, gauge boson and scalar boson. Then it is shown that the contributions from these are large and the allowed parameter space is changed from previous studies.

Neutrinos are very light fermions, a fact that can be well understood if their masses are induced at loop level. Many radiative neutrino mass models have been proposed along the years. The Scotogenic model is a very economical and popular setup that induces Majorana neutrino masses at the 1-loop level and includes a viable dark matter candidate. Based on the original model, many variants can be constructed.
We discuss specific variations of the Scotogenic model with alternative representations under the Standard Model gauge group and additional Scotogenic states, perhaps coming from ultraviolet extended setups. These variants of the Scotogenic paradigm have novel phenomenological predictions and may explain some long-standing anomalies.

The strong CP problem can be solved by parity symmetry. We first review two classes of models: the ones with the minimal fermion content and the ones with the minimal Higgs content. We then focus on the latter class of models and show that the parity symmetry breaking scale is predicted to be the energy scale at which the standard model Higgs quartic coupling vanishes. Surprisingly, after fixing the parity symmetry breaking scale in this way, the gauge coupling constants unify at a high energy scale. We also discuss a model with a dark matter candidate and show that the dark matter direct detection rate is predicted as a function of the standard model parameters.

Twenty years ago, in an experiment at Brookhaven National Laboratory, physicists detected what seemed to be a discrepancy between measurements of the muon’s magnetic moment and theoretical calculations of what that measurement should be, raising the tantalizing possibility of physical particles or forces as yet undiscovered. The Fermilab team has announced that their precise measurement supports this possibility. The reported significance for new physics is 4.2 sigma just slightly below the discovory level of 5 sigma. However, an extensive new calculation of the muon’s magnetic moment using lattice QCD by the BMW-collaboration reduces the gap between theory and experimental measurements. In this talk both the theoretical and experimental aspects are summarized with two possible narratives:
a) almost discovery or b) Standard Model re-inforced. Some details of the lattice caluculation are also shown.

In the first part of this talk, I will discuss sterile neutrino production in modified cosmologies. Although the standard assumption is a radiation dominated universe up to the era of reheating, there are motivated models in which the Hubble rate-temperature relation changes. The abundance of sterile neutrinos produced both resonantly and non-resonantly can be drastically altered with interesting implications for experimental searches. In the second part of my talk, I will present a set of bounds on the primordial black hole (PBH) mass density. By considering stable gas clouds in thermal equilibrium, we can calculate the cooling rate and impose constraints on possible heating processes. Intermediate mass black holes, which can form efficient accretion disks, and light black holes, which emit Hawking radiation, would generate significant amounts of thermal energy. We set limits on the dark matter fraction of PBH as a result and briefly explore the possible contributions from jets. In the final section of the talk, I will discuss two PBH formation models from first order phase transitions. During a first order phase transition, compact remnants in the form of thermal balls and Fermi balls can be formed from particles trapped within the false vacuum. Eventually, after significant cooling, these remnants can collapse into primordial black holes. We consider a delayed formation scenario in which PBH formation occurs after the CMB era. This evades a strong constraint on intermediate mass black holes derived from Planck observations, and opens parameter space for two astrophysically significant populations: BBH progenitors and SMBH seeds. Another PBH formation scenario relies on the decreased pressure forces during a high temperature QCD transition. This produces a peak in the PBH mass distribution at sub-solar mass and even asteroid mass scales, within the PBH mass window.

Gravitational lensing (GL) has been a powerful method to probe matter inhomogeneities in the Universe. GL of gravitational waves, which will be detected in the near future, will enable us to gain more information of the nature of dark matter and further boost the significance of GL. In light of this situation, it is important to have understanding of basic properties of GL. In my talk, I show that gravitational lensing obeys the causality in the sense that (electromagnetic/gravitational) waves emitted from the source arrive at an observer only after the arrival of the signal in geometrical optics. This leads to the Kramers-Kronig relation, a well-known relation in the field of optics, in GL, as the relation between real and imaginary parts of the amplification factor. I will also show some relations which hold as consequence of the Kramers-Kronig relation. Finally, I argue that examining the violation of the Kramers-Kronig relation may be used for correctly extracting the lensing signal in the gravitational wave observations.

Bosonization, in which a fermionic model in 1 + 1 dimensions is transformed to an equivalent bosonic model, has been a powerful technique for the analytical study of many models. However, although the bosonized model is usually much simpler than the original model, obtaining the analytical exact solution is still very hard in some cases.
In this seminar, I present the lattice formulation of the bosonized Schwinger model, which enables us to study the model using the Monte Carlo method. This approach has several distinct advantages over the conventional one based on the original fermionic Lagrangian. First, the approach is unambiguously free from the fermion doubling problem.
Second, it is also free from the sign problem. Moreover, much more efficient configuration generation is possible. I demonstrate the validity of my formulation by showing my numerical results and discuss possible applications to other models.

Ref: H. Ohata, Monte Carlo study of Schwinger model without the sign
problem, arXiv:2303.05481 [hep-lat].

https://www-conf.kek.jp/kincha/
QSTでは、フュージョン（核融合）エネルギーの早期実現に向け、研究開発を実施している。このうち、那珂研究所にある日欧の国際協力で進めるJT-60SAは、フランスに建設中の核融合実験炉ITERの支援研究、その次に発電を行う原型炉のための先端的な運転手法の開発、ITER実験を主導できる研究者・技術者の育成を目的としている。JT-60SAは、旧装置のJT-60Uの施設を最大限再利用するとともに、超伝導コイルなどの新規設備の製作を日欧で分担しており、2013年1月より組立てを開始し、2020年3月に装置が完成した。その後、全てのシステムが設計どおりに連携して機能するかを実証する統合試験運転を進めていたが、2021年3月、コイル通電試験中にコイル接続部での放電による損傷が発生したため、約２年間にわたる改良と試験を行ってきた。初プラズマの達成に必要な性能を確保できたため、今年5月30日より真空排気運転を開始し、統合試験運転を再
開（6月5日にプレス発表）、今年秋の初プラズマ達成を目指している。
講演では、最新のフュージョンエネルギーをめぐる話題とJT-60SAについて取り上げる。

The chiral kinetic theory is a pivotal theoretical tool for the transport theory of massless degrees of freedom. Despite various developments, the usual framework contains only linear-order quantum corrections. In this talk, I will explain the formulation of the chiral kinetic theory with the nonlinear-order corrections. Also I will show several findings from this nonlinear chiral kinetic theory, such as nondissipative transport phenomena, a consistency with the Euler-Heisenberg effective theory and a potential issue on regularization.

Scattering amplitudes are key ingredients for cross sections relevant to collider physics. In the last decade, novel geometric ideas have emerged that hint at a completely different formulation of quantum field theory. For example, the Amplituhedron provides, via geometric means, the all-loop integrand of planar scattering amplitudes in maximally supersymmetric Yang-Mills theory. Unfortunately, dimensional regularization, used conventionally for integration, breaks the beautiful geometric picture. This motivates us in this talk to propose a ‘deformed’ Amplituhedron, which is well-defined in four dimensions. Leveraging four-dimensional integration techniques based on differential equations, we compute the four-particle amplitude up to two loops, as a function of the two deformation parameters. The latter can be interpreted as certain mass and energy variables. We observe simple behaviour in various physical limits of the parameters.