Wave Propagation in Modified Gravity

Abstract

We investigate the propagation of scalar waves induced by matter sources in the context of scalar-tensor theories of gravity which include screening mechanisms for the scalar degree of freedom. The usual approach when studying these theories in the non-linear regime of cosmological perturbations is based on the assumption that scalar waves travel at the speed of light. Within General Relativity such approximation is good and leads to no loss of accuracy in the estimation of observables. We find, however, that mass terms and non-linearities in the equations of motion lead to propagation and dispersion velocities significantly different from the speed of light. As the group velocity is the one associated to the propagation of signals, a reduction of its value has direct impact on the behavior and dynamics of nonlinear structures within modified gravity theories with screening. For instance, the internal dynamics of galaxies and satellites submerged in large dark matter halos could be affected by the fact that the group velocity is smaller than the speed of light. It is therefore important, within such framework, to take into account the fact that different part of a galaxy will see changes in the environment at different times. A full non-static analysis may be necessary under those conditions.

References in corpus (13)

• The relativistic pulsar-white dwarf binary PSR J1738+0333 II. The most stringent test of scalar-tensor gravity
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• Limits of Quasi-Static Approximation in Modified-Gravity Cosmologies
• Unified Dark Matter Scalar Field Models
• Consistent perturbations in an imperfect fluid
• Cosmological tachyon condensation
• Testing the quasi-static approximation in $f(R)$ gravity simulations
• Stronger constraints on non-Newtonian gravity from the Casimir effect
• Jeans analysis in modified gravity
• The Vainshtein mechanism beyond the quasi-static approximation
• On the stability of a galactic disk in modified gravity
• Cosmological simulations with disformally coupled symmetron fields
• Local stability of self-gravitating disks in $f(R)$ gravity

Cited by in corpus (6)

• Speed of Gravitational Waves and the Fate of Scalar-Tensor Gravity
• Gravitational Waves in $F(R)$ Gravity: Scalar Waves and the Chameleon Mechanism
• Cosmic Tsunamis in Modified Gravity: Disruption of Screening Mechanisms from Scalar Waves
• Dynamical Analysis of Screening in Scalar-Tensor Theory
• Tsunamis and Ripples: Effects of Scalar Waves on Screening in the Milky Way
• Galileon Radiation from a Spherical Collapsing Shell