L. Tang - Infinite-temperature coherent dynamics in scarred models

Quantum many-body scars are atypical, athermal eigenstates that reside in the bulk of an otherwise thermalizing spectrum. In many instances, scar towers with uniform energy spacing can be constructed as condensates of identical quasiparticles atop a simple state. Within the scar manifold, the real-time correlation function of the quasiparticle operator exhibits perfect periodic oscillations. Unexpectedly, even though scars constitute a vanishing fraction of the Hilbert space, the correlation function can exhibit underdamped oscillations at a similar frequency even at infinite temperature. In this talk, I show that this originates the approximate dynamical symmetry of the Hamiltonian with respect to the quasiparticle operator, where this symmetry is exact in the scar manifold. Furthermore, I show that the quality factor of the underdamped oscillation can be quantified in terms of the proximity of Hamiltonian to a dynamical symmetry.