Understanding the thermalization process of non-abelian plasmas is of great interest, particularly in cosmology and in relativistic heavy ion collisions. On the one hand, the dynamics of thermalization might have had important consequences at the end of the inflationary epoch in the early Universe. On the other hand, out-of-equilibrium Quantum Chromodynamics (QCD) can nowadays be studied in a repeated and systematic manner in relativistic heavy ion collisions (HICs). For the most part, HICs have been used to characterize the high-temperature phase of QCD, quark-gluon plasma, which behaves as a near-perfect fluid during the period of the collision when the temperature is above the deconfinement transition temperature. Nonetheless, our understanding of the process by which local thermal equilibrium is attained (“hydrodynamization”) in heavy ion collisions affects our interpretation of many observables in such collisions. Therefore, it is crucial to have qualitative and quantitative control over the thermalization/hydrodynamization process of QCD. In this talk, we will discuss a recent development in our understanding of the dynamics of hydrodynamization of Yang-Mills plasmas. Specifically, we focus on the weakly coupled description of a pure glue plasma in the framework of kinetic theory. Due to the nonlinear nature of the kinetic equation, finding intuitive and systematic organizing principles to study the dynamics of the distribution function starting from arbitrary initial conditions has proved to be challenging. Adiabatic Hydrodynamization is a novel framework that aims to provide such an organizing principle by identifying the long-lived solutions of the theory as the low-energy eigenstates of the time evolution operator of the theory (the “Hamiltonian”), provided that the (time-dependent) basis on which the Hamiltonian is formulated be such that the evolution is adiabatic. We work this out explicitly in a simplified version of QCD kinetic theory in a geometry motivated by HIC experiments. We conclude by laying out the prospects for studying more general kinetic theories in this framework.

Light hypothetical particles with masses up to O(100) MeV can be produced in the core of supernovae. Their subsequent decays to neutrinos can produce a flux component with higher energies than the standard flux. We study the impact of heavy neutral leptons, Z′bosons, in particular U(1)Lμ−Lτ and U(1)B−L gauge bosons, and majorons coupled to neutrinos flavor-dependently. We obtain new strong limits on these particles from no events of high-energy SN 1987A neutrinos and their future sensitivities from observations of galactic supernova neutrinos.

https://www-conf.kek.jp/kincha/
低エネルギー有効場の理論のうちで、量子重力と無矛盾に結合できるものをLandscape、できないものをSwamplandと呼ぶ。LandscapeとSwamplandを分類する問題は量子重力の沼地問題と言い、近年よく研究されている。本講演では、沼地問題のいくつかの予想とその証拠・証明あるいは応用についてお話ししたい。

Conformal field theories are characterized by structure constants (3-point correlation functions). In order for the theory to be consistent, the structure constants must satisfy the “bootstrap equation”, which is useful to numerically solve, for example, for the critical exponent of the 3d Ising model. From a mathematical point of view, the bootstrap equation arises from the operad structure of spacetime, and such mathematics may be useful to find (as yet undiscovered) constraints on quantum field theory. In this talk, we will introduce the notion of operad and discuss the relation between operads and operator product expansions based on mathematical studies of conformal field theories in two dimensions.

The IKKT matrix model is viewed as a gauge theory of space-time and matter, which arises through an analog of the Higgs effect on suitable vacua, describing 3+1 dimensional space-time branes in the weak coupling regime. In particular, we consider vacua where the SO(9,1) invariance is spontaneously broken to SO(3,1). These vacua describe a cosmological FLRW space-time, on which (an extended version of) gravity arises through quantum effects. Some progress towards understanding the resulting physics is discussed.

On February 23, 1987, neutrinos from a supernova explosion in the Large Magellanic Cloud were observed for the first time in the world. Observations of supernova neutrinos, which are emitted from supernova explosions caused by gravitational collapse at the center of massive stars during the final stage of their evolution, are important for various topics in astrophysics, including the history of star formation and the mechanism of supernova explosions. Therefore, supernova neutrinos have been actively studied both observationally and theoretically. In particular, Super-Kamiokande, which which began a new stage of operations as SK-Gd in 2020, is expected to bring drastic progress in supernova neutrino research, especially in the measurement of diffuse supernova neutrino background and the pointing accuracy for nearby supernovae. Furthermore, next-generation large neutrino detectors such as Hyper-Kamiokande will enter a new stage of precision measurements for supernova neutrino observations.
In this seminar, I will discuss recent progress and prospects of supernova neutrino research.

The strong CP problem can be solved by parity symmetry with extended gauge 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 discuss a dark matter model where the stability of dark matter accidentally arrises from the extended gauge symmetry. The enough stability of dark matter provides an upper bound on the parity symmetry breaking scale. We then discuss a neutrino mass model and show that in the minimal model the neutrino mass is generated by quantum corrections. New gauge-singlet fermions in the model may be discovered by near-future experiments.

Neutrinoless double beta decay is the primary means with which we can probe a potential Majorana nature of light neutrinos. Planned experiments searching for this hypothetical decay aim to be sensitive to half-lives of up to 10^28 years, allowing to probe Majorana neutrino mass scales of O(10 meV). It is also well established that neutrinoless double beta decay receives contributions beyond light neutrino exchange in New Physics scenarios beyond the Standard Model (SM) that incorporate lepton number violation, such as sterile Majorana neutrinos and R-Parity violating supersymmetry. After briefly reviewing neutrinoless double beta decay and its interpretations, I will motivate the use of two-neutrino double beta decay to probe for exotic physics as well. This decay, allowed in the SM and observed in several isotopes, is typically considered background to neutrinoless double beta decay searches. Besides allowing insights into nuclear matrix elements it can also be used to search for New Physics, though, due to high event statistics in current and future double beta decay searches. In this context, I will discuss modifications of the double beta decay spectrum due to exotic particle emission (such as kinks from sterile neutrinos), exotic currents beyond V-A and neutrino self-interactions, motivating the search for such scenarios.

I will discuss the role of inclusive and exclusive b-> c(u) l nu decays in the extractions of $|V_{cb}|$ and $|V_{ub}|$. I will update the precision extractions of the observables associated with a few related exclusive decay modes. Also, I will focus on the possible role of the available data on these decays in constraining the parameters associated with the new interactions beyond the SM.

Universal dynamics associated with scale-invariant properties has garnered much attention in the field of statistical mechanics for a long time. Thanks to the high controllability of ultracold atom experiments, such universal quantum dynamics has been studied theoretically and experimentally over a decade from the perspective of nonthermal fixed points, which was originally introduced in the context of high-energy physics. In this talk, we will begin with an introduction to ultracold atoms, reviewing applications of nonthermal fixed points to ultracold atoms by showing recent theoretical and experimental achievements.