Phase transitions as a manifestation of spontaneous unitarity violation

TL;DR

This paper proposes that the emergence of a specific ordered state during phase transitions is a manifestation of spontaneous unitarity violation in quantum dynamics, challenging traditional symmetry-breaking paradigms.

Contribution

It introduces a novel perspective that phase transitions reflect spontaneous unitarity violation, linking dynamical symmetry breaking to fundamental quantum evolution.

Findings

Phase transitions can be viewed as spontaneous unitarity violations.

The emergence of a global order parameter is incompatible with unitary evolution.

Schrödinger's equation becomes unstable for macroscopic objects due to thermodynamic limits.

Abstract

Spontaneous symmetry breaking is well understood under equilibrium conditions as a consequence of the singularity of the thermodynamic limit. How a single global orientation of the order parameter dynamically emerges from an initially symmetric state during a phase transition, however, is not captured by this paradigm. Here, we present a series of symmetry arguments suggesting that singling out a global choice for the ordered state is in fact forbidden under unitary time evolution, even in the presence of an environment and infinitesimal symmetry breaking perturbrations. We thus argue that the observation of phase transitions in our everyday world presents a manifestation of the unitarity of quantum dynamics itself being spontaneously broken. We argue that this agrees with the observation that Schr\"odinger's time dependent equation is rendered unstable for macroscopic objects owing to the same singular thermodynamic limit that affects equilibrium configurations.