Axion misalignment as a synchronization phenomenon

Abstract

We propose a dynamical reinterpretation of axion misalignment as an emergent collective phenomenon. Drawing an explicit parallel between axion field dynamics and synchronization in coupled oscillator systems, we show that a macroscopic axion phase can arise dynamically from initially incoherent configurations through gradient-driven ordering in an expanding Universe. In this framework, the misalignment angle is not a fundamental initial condition but a collective variable that becomes well defined only once phase coherence develops. Using a three-dimensional lattice study with full second-order dynamics, we show that this collective phase is selected prior to the onset of axion oscillations in the regimes studied, providing dynamical support for the standard misalignment picture. This perspective offers a new way of organizing axion initial-condition sensitivity and reframes small-angle assumptions in terms of the efficiency of phase ordering in the early Universe.

8 pages, 4 figures