Emergent geometries and nonlinear-wave dynamics in photon fluids

TL;DR

This paper explores how nonlinear wave interactions in photon fluids create emergent curved spacetime geometries, leading to phenomena like shock formation, and offers a novel analogue gravity model beyond kinematic descriptions.

Contribution

It introduces an emergent spacetime framework for photon fluids, linking nonlinear wave dynamics to analogue gravity and shock formation.

Findings

Wave self-steepening leads to shock formation.

Emergent spacetime geometry influences wave dynamics.

Analogue gravity model extends beyond kinematic descriptions.

Abstract

Nonlinear waves in defocusing media are investigated in the framework of the hydrodynamic description of light as a photon fluid. The observations are interpreted in terms of an emergent curved spacetime generated by the waves themselves, which fully determines their dynamics. The spacetime geometry emerges naturally as a result of the nonlinear interaction between the waves and the self-induced background flow. In particular, as observed in real fluids, different points of the wave profile propagate at different velocities leading to the self-steepening of the wave front and to the formation of a shock. This phenomenon can be associated to a curvature singularity of the emergent metric. Our analysis offers an alternative insight into the problem of shock formation and provides a demonstration of an analogue gravity model that goes beyond the kinematic level.