Keio University · Physics and Astronomy
Professor Ryo Yokokura's research lab specializes in quantum field theory and topological phases of matter, with a focus on higher-form symmetries, higher-group structures, and non-invertible symmetries in (3+1)-dimensional quantum field theories. The lab investigates axion electrodynamics, topological field theories, and emergent symmetries in gapped and gapless systems, particularly in the context of anomalies, spontaneous symmetry breaking, and topological order. A central theme is the interplay between global symmetries—especially higher-form and non-invertible symmetries—and topological excitations such as domain walls, anyons, and linked worldlines.
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We study higher-form symmetries in a low-energy effective theory of a massless axion coupled with a photon in (3+1) dimensions. It is shown that the higher-form symmetries of this system are accompanied by a semistrict 3-group (2-crossed module) structure, which can be found by the correlation functions of symmetry generators of the higher-form symmetries. We argue that the Witten effect and anomalous Hall effect in the axion electrodynamics can be described in terms of 3-group transformations.
We study higher-form global symmetries and a higher-group structure of a low-energy limit of $(3+1)$-dimensional axion electrodynamics in a gapped phase described by a topological action. We argue that the higher-form symmetries should have a semi-strict 4-group (3-crossed module) structure by consistency conditions of couplings of the topological action to background gauge fields for the higher-form symmetries. We find possible 't Hooft anomalies for the 4-group global symmetry, and discuss phy
We study non-invertible global symmetries in $(3+1)$-dimensional axion electrodynamics with a massless axion and a massless photon. In addition to a previously known non-invertible 0-form shift symmetry of the axion, we find a non-invertible 1-form symmetry associated with the equation of motion for the photon. Correlation functions of non-invertible symmetry defects lead to invertible 1- and 2-form symmetry defects associated with Bianchi identities for the axion and photon. In terms of the cor
We show that axion models with the domain wall number k in (3+1) dimensions, i.e., periodic scalar field theories admitting k axion domain walls, exhibit an emergent Zk 3-form symmetry for k>1 in addition to a conventional Zk 0-form symmetry. The emergent 3-form symmetry is explicitly shown by establishing a low-energy dual transformation between the scalar field theory and a 3-form gauge theory. We further argue that the emergent 3-form symmetry is spontaneously broken, and the breaking pattern
A bstract We demonstrate a universal mechanism of a class of instabilities in infrared regions for massless Abelian p -form gauge theories with topological interactions, which we call generalized chiral instabilities. Such instabilities occur in the presence of initial electric fields for the p -form gauge fields. We show that the dynamically generated magnetic fields tend to decrease the initial electric fields and result in configurations with linking numbers, which can be characterized by non
We study higher-form symmetries and a higher group in the low energy limit of a (3+1)-dimensional axion electrodynamics with a massive axion and a massive photon. A topological field theory describing topological excitations with the axion-photon coupling, which we call a topological axion electrodynamics, is obtained in the low energy limit. Higher-form symmetries of the topological axion electrodynamics are specified by equations of motion and Bianchi identities. We find that there are induced
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