Nonlocal Gravity: Damping of Linearized Gravitational Waves

TL;DR

This paper shows that in nonlocal gravity, gravitational waves experience exponential damping due to gravitational memory effects, with damping times comparable to the universe's age, suggesting potential observational implications.

Contribution

It demonstrates the dissipative nature of nonlocal gravity and estimates the damping timescale for gravitational waves within this framework.

Findings

Gravitational waves are exponentially damped in nonlocal gravity.

Damping timescales are comparable to the age of the universe.

Nonlocal gravity introduces a gravitational memory drag effect.

Abstract

In nonlocal general relativity, linearized gravitational waves are damped as they propagate from the source to the receiver in the Minkowski vacuum. Nonlocal gravity is a generalization of Einstein's theory of gravitation in which nonlocality is due to the gravitational memory of past events. That nonlocal gravity is dissipative is demonstrated in this paper within certain approximation schemes. The gravitational memory drag leads to the decay of the amplitude of gravitational waves given by the exponential damping factor exp (-t/\tau), where $\tau$ depends on the kernel of nonlocal gravity. The damping time $\tau$ is estimated for gravitational waves of current observational interest and is found to be of the order of, or longer than, the age of the universe.