Gravitational Landau Damping for massive scalar modes

TL;DR

This paper demonstrates that gravitational scalar waves can undergo Landau damping in a non-collisional particle gas, with damping occurring only for subluminal phase velocities, supported by analytical and numerical analysis.

Contribution

It establishes the first analytical and numerical demonstration of Landau damping for gravitational scalar modes in relativistic media.

Findings

Damping occurs only if phase velocity is subluminal.

Analytical determination of damping rate from Vlasov equation.

Numerical analysis confirms damping in cosmological settings.

Abstract

We establish the possibility of Landau damping for gravitational scalar waves which propagate in a non-collisional gas of particles. In particular, under the hypothesis of homogeneity and isotropy, we describe the medium at the equilibrium with a J\"uttner-Maxwell distribution, and we analytically determine the damping rate from the Vlasov equation. We find that damping occurs only if the phase velocity of the wave is subluminal throughout the propagation within the medium. Finally, we investigate relativistic media in cosmological settings by adopting numerical techniques.