Nonlocal action for long-distance modifications of gravity theory

TL;DR

This paper develops a covariant nonlocal gravity action aimed at addressing cosmological constant and acceleration issues, highlighting its curvature-based structure and implications for causality.

Contribution

It introduces a covariant nonlocal action for long-distance gravity modifications, emphasizing its curvature expansion and compatibility with causality.

Findings

Nonlocal action constructed for modified gravity

Curvature-squared terms form the basis of the action

Nonlocal form factors relate to quantum and brane effects

Abstract

We construct the covariant nonlocal action for recently suggested long-distance modifications of gravity theory motivated by the cosmological constant and cosmological acceleration problems. This construction is based on the special nonlocal form of the Einstein-Hilbert action explicitly revealing the fact that this action within the covariant curvature expansion begins with curvature-squared terms. Nonlocal form factors in the action of both quantum and brane-induced nature are briefly discussed. In particular, it is emphasized that for certain class of quantum initial value problems nonlocal nature of the Euclidean action does not contradict the causality of effective equations of motion.