Yuta Kikuchi

Vacuum structure of bifundamental gauge theories at finite topological angles

A bstractWe discuss possible vacuum structures of SU(n) × SU(n) gauge theories with bifundamental matters at finite θ angles. In order to give a precise constraint, a mixed ’t Hooft anomaly is studied in detail by gauging the center ℤn one-form symmetry of the bifundamental gauge theory. We propose phase diagrams that are consistent with the con-straints, and also give a heuristic explanation of the result based on the dual superconductor scenario of confinement.

Relativistic Causal Hydrodynamics Derived from Boltzmann Equation: a novel reduction theoretical approach

We derive the second-order hydrodynamic equation and the microscopic formulae of the relaxation times as well as the transport coefficients systematically from th e relativistic Boltzmann equation. Our derivation is based on a novel development of the renormalization-group method, a powerful reduction theory of dynamical systems, which has been applied successfully to derive the non-relativistic second-order hydrodynamic equation Our theory nicely gives a compact expression of the deviation of the distribution function in terms of the linearized collision operator, which is different from those used as an ansatz in the conventional fourteenmoment method. It is confirmed that the resultant microscopi c expressions of the transport coefficients coincide with those derived in the Chapman-Enskog expansion method. Furthermore, we show that the microscopic expressions of the relaxation times have natural and physically plausible forms. We prove that the propagating velocities of the fluctuations of the hydrodynamical variab les do not exceed the light velocity, and hence our seconder-order equation ensures the desired causality. It is also confirmed that the equilibrium state is stable for any perturbation described by our equation.

Derivation of second-order relativistic hydrodynamics for reactive multicomponent systems

We derive the second-order hydrodynamic equation for reactive multi-component systems from the relativistic Boltzmann equation. In the reactive system, particles can change their species under the restriction of the imposed conservation laws during the collision process. Our derivation is based on the renormalization group (RG) method, in which the Boltzmann equation is solved in an organized perturbation method as faithfully as possible and possible secular terms are resummed away by a suitable setting of the initial value of the distribution function. The microscopic formulae of the relaxation times and the lengths are explicitly given as well as those of the transport coefficients for the reactive multi-component system. The resultant hydrodynamic equation with these formulae has nice properties that it satisfies the positivity of the entropy production rate and the Onsagers reciprocal theorem, which ensure the validity of our derivation.

Topological Properties of the Chiral Magnetic Effect in Multi-Weyl Semimetals

We compute the chiral magnetic effect (CME) in multi-Weyl semimetals (multi-WSMs) based on the chiral kinetic theory. Multi-WSMs are WSMs with multiple monopole charges that have nonlinear and anisotropic dispersion relations near the Weyl points, and we need to extend the conventional computation of the CME in WSMs with linear dispersion relations. The topological properties of the CME in multi-WSMs are investigated in detail for not only static magnetic fields but also time-dependent (dynamic) ones. We propose an experimental setup to measure the multiple monopole charge via the topological nature hidden in the dynamic CME.

Effective field theory and the scattering process for magnons in ferromagnets, antiferromagnets, and ferrimagnets

We discuss that a low-energy effective Lagrangian relying on SO(3)

Global inconsistency, 't Hooft anomaly, and level crossing in quantum mechanics

\rightarrow

Anomaly matching for the phase diagram of massless

SO(2) is applicable for a ferrimagnet as well as a ferromagnet and an antiferromagnet. The analysis of the particle states shows that there exist not only massless modes with the dispersion relations

\mathbb{Z}_N

\omega \propto |\bm{k}|,\, |\bm{k}|^2

-QCD

, i.e., the so-called type-I and type-II Nambu-Goldstone modes, respectively, but also gapped modes with

Anomaly matching for the phase diagram of massless ZN-QCD

\omega \propto m^2+|\bm{k}|^2