Quasi-Nambu-Goldstone modes in many-body scar models

TL;DR

This paper demonstrates the universal presence of quasi-Nambu-Goldstone modes in many-body scar models, arising from quasisymmetry rather than traditional symmetry, especially in the degenerate energy limit.

Contribution

It introduces the concept of quasi-Nambu-Goldstone modes in many-body scar models and links them to quasisymmetry, expanding understanding of collective excitations.

Findings

Universal existence of collective modes in scar models at degeneracy

Number and quantum numbers of modes determined by quasisymmetry

Analogy established between spontaneous symmetry breaking and scar physics

Abstract

From the quasisymmetry-group perspective [Phys. Rev. Lett. 126, 120604 (2021)], we show the universal existence of collective, coherent modes of excitations in many-body scar models in the degenerate limit, where the energy spacing in the scar tower vanishes. The number of these modes, as well as the quantum numbers carried by them, are given, not by the symmetry of the Hamiltonian, but by the quasisymmetry of the scar tower: hence the name quasi-Nambu-Goldstone modes. Based on this, we draw a concrete analogy between the paradigm of spontaneous symmetry breaking and the many-body scar physics in the degenerate limit.