Gravitational waves in Modified Gauss-Bonnet Gravity

TL;DR

This paper investigates gravitational wave properties in modified Gauss-Bonnet gravity, deriving wave equations, confirming the speed of tensor modes equals light speed, and identifying an additional massive scalar mode influenced by background curvature.

Contribution

It provides explicit wave equations in modified Gauss-Bonnet gravity and analyzes the scalar mode mass dependence on background curvature, extending gravitational wave theory beyond general relativity.

Findings

Tensor mode speed equals the speed of light

An extra massive scalar mode exists in gravitational wave propagation

Scalar mode mass varies with background curvature

Abstract

We study the gravitational waves in modified Gauss-Bonnet gravity. Applying the metric perturbation around a cosmological background, we obtain explicit expressions for the wave equations. It is shown that the speed of the traceless mode is equal to the speed of light. An additional massive scalar mode appears in the propagation of the gravitational waves. To find phenomena beyond the general relativity the scalar mode mass is calculated as a function of the background curvature in some typical models.