Cosmic Tsunamis in Modified Gravity: Disruption of Screening Mechanisms from Scalar Waves

TL;DR

This paper investigates how scalar waves in modified gravity theories can disrupt screening mechanisms, potentially undermining the theories' consistency with observations.

Contribution

It demonstrates through simulations that scalar waves can significantly weaken screening mechanisms in modified gravity models, challenging their viability.

Findings

Scalar waves can amplify fifth forces by several orders of magnitude.

Waves in the symmetron model disrupt screening, affecting observational constraints.

Screening mechanisms may be less effective in dynamic environments with scalar waves.

Abstract

Extending general relativity by adding extra degrees of freedom is a popular approach for explaining the accelerated expansion of the Universe and to build high energy completions of the theory of gravity. The presence of such new degrees of freedom is, however, tightly constrained from several observations and experiments that aim to test general relativity in a wide range of scales. The viability of a given modified theory of gravity, therefore, strongly depends on the existence of a screening mechanism that suppresses the extra degrees of freedom. We perform simulations, and find that waves propagating in the new degrees of freedom can significantly impact the efficiency of some screening mechanisms, thereby threatening the viability of these modified gravity theories. Specifically, we show that the waves produced in the symmetron model can increase the amplitude of the fifth force and the parametrized post-Newtonian parameters by several orders of magnitude.