Title: Symmetry re-breaking in an effective theory of quantum coarsening
Abstract: Rydberg simulators, superconducting qubit arrays and other quantum simulation platforms are increasingly able to simulate isolated quantum many-body dynamics in two spatial dimensions, and explore uncharted territory for theory. For example, recent experiments study order parameter dynamics in both slow ramps and (fast) quenches involving phase transitions, thereby placing the physics of quantum coarsening in the experimental realm. We present a simple model accounting for two central observations in one of these recent experiments [T. Manovitz et al., Nature 638, 86 (2025)]: an apparent acceleration of the coarsening process, rather than critical slowing down, as the quantum critical point is approached; and persistent oscillations in both order parameter and correlation length following quenches from deep within the ordered phase. Surprisingly, we find that these features neither require coherent quantum dynamics, nor are they tied to the long-time coarsening process. Our model identifies the energy-conserving dynamics as central actor. This engenders a temporally structured thermalization process which culminates in what we term symmetry re-breaking, a robust phenomenon wherein the order parameter can switch direction without the system ever leaving the symmetry-broken phase.