Degravitation, Orbital Dynamics and the Effective Barycentre

TL;DR

This paper introduces a modified gravity theory where Newton's constant is a covariant operator, exploring its cosmological implications and effects on orbital dynamics, including the effective barycentre, with results reducing to general relativity in the appropriate limit.

Contribution

The paper proposes a covariant nonlocal gravity model that degravitate vacuum energy and analyzes its impact on cosmology and orbital dynamics, including the effective barycentre.

Findings

Modified orbital dynamics for binary systems.

Effective 1.5 post-Newtonian barycentre derived.

Results recover general relativity when nonlocal parameters vanish.

Abstract

In this article we present a particular theory of gravity in which Einstein's field equations are modified by promoting Newton's constant $G$ to a covariant differential operator $G_\Lambda(\Box_g)$. The general idea was obviously outlined for the first time in [13-16] and originates from the quest of finding a mechanism that is able to degravitate the vacuum energy on cosmological scales. We suggest in this manuscript a precise covariant coupling model which acts like a high-pass filter with a macroscopic distance filter scale $\sqrt{\Lambda}$. In the context of this specific theory of gravity we review some cosmological aspects before we briefly recall the effective relaxed Einstein equations outlined for the first time in [1]. We present a general procedure to determine the gravitational potentials for a far away wave zone field point. Moreover we work out the modified orbital dynamics of a binary-system as well as the effective 1.5 post-Newtonian barycentre for a generic $n$-body system. We notice that it is always possible to recover the corresponding general relativistic results in the limit of vanishing nonlocal modification parameters.