Hydrodynamics as the effective field theory of strong-to-weak spontaneous symmetry breaking

Fuente: arXiv
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Autori principali: Huang, Xiaoyang, Qi, Marvin, Zhang, Jian-Hao, Lucas, Andrew
Natura: Preprint
Pubblicazione: 2024
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author Huang, Xiaoyang
Qi, Marvin
Zhang, Jian-Hao
Lucas, Andrew
author_facet Huang, Xiaoyang
Qi, Marvin
Zhang, Jian-Hao
Lucas, Andrew
contents Inspired by the hunt for new phases of matter in quantum mixed states, it has recently been proposed that the equivalence of microcanonical and canonical ensembles in statistical mechanics is a manifestation of strong-to-weak spontaneous symmetry breaking (SWSSB) in an underlying many-body quantum description. Here, we build an effective field theory for SWSSB of a global U(1) symmetry; the answer exactly reproduces the Schwinger-Keldysh effective field theory of diffusion for the conserved charge. We conclude that hydrodynamics can be understood as a theory of "superfluidity" for the broken strong symmetry: a non-vanishing susceptibility is a measurable order parameter for SWSSB, the diffusion mode is the Goldstone boson of the spontaneously broken continuous symmetry, and a generalization of Goldstone's Theorem implies that the diffusion mode is always long-lived. This perspective provides a transparent physical explanation for the unusual "reparameterization" symmetries which are a necessary ingredient of Schwinger-Keldysh effective field theories for "normal fluids".
format Preprint
id arxiv_https___arxiv_org_abs_2407_08760
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Hydrodynamics as the effective field theory of strong-to-weak spontaneous symmetry breaking
Huang, Xiaoyang
Qi, Marvin
Zhang, Jian-Hao
Lucas, Andrew
Strongly Correlated Electrons
Quantum Gases
Statistical Mechanics
Quantum Physics
Inspired by the hunt for new phases of matter in quantum mixed states, it has recently been proposed that the equivalence of microcanonical and canonical ensembles in statistical mechanics is a manifestation of strong-to-weak spontaneous symmetry breaking (SWSSB) in an underlying many-body quantum description. Here, we build an effective field theory for SWSSB of a global U(1) symmetry; the answer exactly reproduces the Schwinger-Keldysh effective field theory of diffusion for the conserved charge. We conclude that hydrodynamics can be understood as a theory of "superfluidity" for the broken strong symmetry: a non-vanishing susceptibility is a measurable order parameter for SWSSB, the diffusion mode is the Goldstone boson of the spontaneously broken continuous symmetry, and a generalization of Goldstone's Theorem implies that the diffusion mode is always long-lived. This perspective provides a transparent physical explanation for the unusual "reparameterization" symmetries which are a necessary ingredient of Schwinger-Keldysh effective field theories for "normal fluids".
title Hydrodynamics as the effective field theory of strong-to-weak spontaneous symmetry breaking
topic Strongly Correlated Electrons
Quantum Gases
Statistical Mechanics
Quantum Physics
url https://arxiv.org/abs/2407.08760