Weaker Gravity at Submillimetre Scales in Braneworld Models

TL;DR

This paper explores braneworld models with additional curvature couplings, showing that under certain conditions, gravity weakens at short distances, which has implications for cosmology and stellar stability.

Contribution

It introduces braneworld models with Gauss-Bonnet and Einstein-Hilbert terms that lead to weaker gravity at small scales, contrasting with previous predictions of stronger gravity.

Findings

Gravity weakens at short distances in these models.

The models are compatible with cosmological observations.

Stability of compact stars is discussed.

Abstract

Braneworld models typically predict gravity to grow stronger at short distances. In this paper, we consider braneworlds with two types of additional curvature couplings, a Gauss-Bonnet term in the bulk, and an Einstein-Hilbert (EH) term on the brane. In the regime where these terms are dominant over the bulk EH term, linearized gravity becomes weaker at short distances on the brane. In both models, the weakening of gravity is tied to the presence of ghosts in the graviton mass spectrum. We find that the ordinary coupling of matter to gravity is recovered at low energies/long wavelengths on the brane. We give some implications for cosmology and show its compatibility with observations. We also discuss the stability of compact stars.