Spherically symmetric brane in a bulk of f(R) and Gauss-Bonnet Gravity

TL;DR

This paper derives and compares static spherically symmetric solutions for a brane in five-dimensional bulk gravity theories, including Einstein-Hilbert, Gauss-Bonnet, and f(R) modifications, revealing how these corrections alter horizon structures.

Contribution

It provides new exact solutions for brane-world models with Gauss-Bonnet and f(R) corrections, and demonstrates their consistency across different solution methods.

Findings

Gauss-Bonnet correction modifies horizon locations.

Solutions from perturbative and exact methods match.

f(R) gravity with Gauss-Bonnet term affects spacetime structure.

Abstract

Effective gravitational field equations on a four dimensional brane embedded in a five dimensional bulk have been considered. Using the Einstein-Hilbert action along with the Gauss-Bonnet correction term, we have derived static spherically symmetric vacuum solution to the effective field equations, first order in the Gauss-Bonnet coupling parameter. The solution so obtained, has one part corresponding to general relativity with an additional correction term, proportional to the Gauss-Bonnet coupling parameter. The correction term modifies the spacetime structure, in particular, the location of the event horizon. Proceeding further, we have derived effective field equations for $f(R)$ gravity with Gauss-Bonnet correction term and a static spherically symmetric solution has been obtained. In this case the Gauss-Bonnet term modifies both the event and cosmological horizon of the spacetime. There exist another way of obtaining the brane metric --- expanding the bulk gravitational field equations in the ratio of bulk to brane curvature scale and assuming a separable bulk metric ansatz. It turns out that static, spherically symmetric solutions obtained from this perturbative method can be matched exactly, with the solutions derived earlier. This will hold for Einstein-Hilbert plus Gauss-Bonnet as well as for f(R) with the Gauss-Bonnet correction. Implications of these results are discussed.