Seminars

ハドロン物理セミナーでは、気鋭の研究者に最近の研究のお話をしていただきます。

We invite spirited researchers as speakers of the Hadron Physics Seminar.

*  以下の時間は、UTC + 9である日本標準時（JST）です。

*  The schedule below is in terms of Japan Standard Time (JST), namely UTC +9.

Tue, December 23rd

Lattice Gradient Flows and Their Application to the ’t Hooft Loop

Hiromasa Watanabe (Keio Univ.)
Room 907 (17:00-18:30)

Abstract: We investigate the stability of the topological charge under gradient flow, taking the admissibility condition into account. For SU(2) theory with the Wilson action, we numerically demonstrate that gradient flow with the DBW2 gauge actions significantly stabilizes the topological sectors and exhibits a rapid convergence to each sector. The (in)stability is closely related to the behavior of instanton size along flows, which depends on the choice of the flow action. The latter property is advantageous in various applications, and one such example is the computation of the ’t Hooft loop on the lattice. The 't Hooft loop plays an important role in classifying the confining vacuum structures of gauge theory, comparable to the Wilson loop. Motivated by recent developments in generalized symmetries and anomalies, we are performing lattice simulations to confirm that the characterization, known as the Wilson-'t Hooft classification, holds nonperturbatively. In the seminar, we discuss how to implement the loop operator on the lattice and show preliminary results.

Mon, December 15th

Late-Time Behavior of Correlation Functions in Fluctuating Hydrodynamics

Dong-Lin Wang (USTC)
Room 907 (16:30-18:30)

Abstract: Fluctuations are intrinsic to dissipative systems, as dictated by the fluctuation-dissipation theorem. In hydrodynamics, fluctuation effects enter correlation functions through loop corrections. However, no universal expression exists for these corrections, as they depend on the type of the stochastic noises and interactions. In this work, we present general results for two-point correlation functions in both linear and nonlinear fluctuating hydrodynamics. In the linear case, we show that fluctuation-induced corrections can be consistently regularized to zero. In nonlinear cases, we find a general late-time behavior of the two-point correlation functions by analyzing the singularities of the associated loop integrals.

Mon, December 1st

Tripling fluctuations in the hadron-quark crossover: Insights from ultracold atomic physics

Hiroyuki Tajima (The University of Tokyo)
Room 907 (16:30-18:00)

Abstract: Elucidating the properties of dense matter in a massive neutron star is one of the most important topics in nuclear astrophysics. Recent astrophysical observations suggest a possibility of a smooth crossover from the low-density hadron phase to the high-density quark phase, known as the hadron-quark crossover scenario. However, its microscopic mechanism is still under debate. In this talk, we approach this problem from the perspective of ultracold atomic physics, where a similar crossover phenomenon, that is, Bose-Einstein condensate (BEC)-Bardeen-Cooper-Schrieffer (BCS) crossover, has been established through state-of-the-art experiments. By analogy with pairing fluctuations that are crucial in the BEC-BCS crossover, we discuss the role of “tripling” fluctuations in the hadron-quark crossover.