On brane-induced gravity in warped backgrounds

TL;DR

This paper investigates the possibility of modifying gravity at large distances within warped brane-world models featuring brane-induced terms, identifying regions with viable weakly coupled gravity and others with problematic ghost fields.

Contribution

It analyzes the parameter space of warped brane models with induced gravity, revealing conditions for consistent large-distance modifications and the emergence of ghost radion modes.

Findings

Three regions where the theory remains weakly coupled up to high energies.

One region where gravity is four-dimensional at all scales due to induced Einstein term.

Two regions where gravity behavior changes at ultra-large distances with ghost radion modes.

Abstract

We study whether modification of gravity at large distances is possible in warped backgrounds with two branes and a brane-induced term localized on one of the branes. We find that there are three large regions in the parameter space where the theory is weakly coupled up to high energies. In one of these regions gravity on the brane is four-dimensional at arbitrarily large distances, and the induced Einstein term results merely in the renormalization of the 4d Planck mass. In the other two regions the behavior of gravity changes at ultra-large distances; however, radion becomes a ghost. In parts of these regions, both branes have positive tensions, so the only reason for the appearance of the ghost field is the brane-induced term. In between these three regions, there are domains in the parameter space where gravity is strongly coupled at phenomenologically unacceptable low energy scale.