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Keito Shimizu

Publications and source records attributed to Keito Shimizu.

4 recordsLinked to original sources
arXiv2026

Revisiting boundary electromagnetic duality and edge modes

We revisit electric and magnetic surface charges and edge modes in four-dimensional Maxwell theory and QED on a spacetime with a finite spatial boundary. Using the S-wall, which implements electromagnetic duality, we clarify the dual structure of surface charges. We show that, for the standard Neumann and Dirichlet boundary conditions, large gauge transformations and the corresponding shifts of edge modes are gauge redundancies rather than physical boundary symmetries. We also consider singular large gauge transformations and interpret them as insertions of Wilson or 't Hooft loops on the boundary. For modified boundary conditions, we show that large gauge transformations can become genuine physical boundary symmetries generated by topological surface operators, and that the corresponding edge modes can become physical. We further construct new boundary conditions that are electromagnetic duals of the modified boundary conditions.

hep-th↗
arXiv2025

Functional Renormalization Group Analysis of $O(3)$ Nonlinear Sigma Model and Non-Abelian Bosonization Duality

It is known that the $U(2)$ Wess-Zumino-Witten model is dual to the free fermion theory in two dimensions via non-Abelian bosonization. While it is decomposed into the $SU(2)$ Wess-Zumino-Witten model and a free compact boson, the former is believed to be equivalent to the $O(3)$ nonlinear sigma model with the theta term at $θ=π$. In this work, we reexamine this duality through the lens of non-perturbative renormalization group (RG) flow. We analyze the RG flow structure of the $O(3)$ nonlinear sigma model with the theta term in two dimensions using the functional renormalization group. Our results reveal a nontrivial fixed point with a nonzero value of the topological coupling. The scaling dimensions (critical exponents) at this fixed point suggest the realization of a duality between the $O(3)$ nonlinear sigma model with the theta term and the free fermion theory, indicating that these models belong to the same universality class.

hep-th↗
arXiv2024

Heat and work in black hole thermodynamics via holography

We propose a formulation of black hole thermodynamics that incorporates the notions of heat and work, based on the thermodynamics in quantum theory and the AdS/CFT correspondence. First, for coupled holographic CFTs, we define a coarse-graining procedure adopting the principle of maximum entropy. Employing this approach, when the system is divided into a target system and thermal baths, we formulate the first and second laws, as well as the fundamental thermodynamic relation. Then, by translating the resulting thermodynamics into the AdS gravity language, we construct a thermodynamic framework for composite black hole systems that encompasses both heat and work. This formulation relies on holography, but not on energy conditions on the gravity side. We also argue that the second law serves as a necessary criterion for the UV completeness of gravitational theories.

hep-th↗