Brane-induced gravity in more than one extra dimensions: violation of equivalence principle and ghost

TL;DR

This paper investigates a brane-induced gravity model with multiple extra dimensions, revealing violations of the equivalence principle and the presence of ghost fields, which challenge the model's consistency.

Contribution

It analyzes the linearized theory of multi-dimensional brane gravity, identifying equivalence principle violations and ghost fields, extending previous models like GRS.

Findings

Violation of gravitational and inertial mass equivalence.

Existence of a localized ghost scalar field.

Four-dimensional gravity mimics tensor structure at intermediate scales.

Abstract

We consider brane-induced gravity model in more than one extra dimensions, regularized by assuming that the bulk gravity is soft in ultraviolet. We study linear theory about flat multi-dimensional space-time and flat brane. We first find that this model allows for violation of equivalence between gravitational and inertial masses of brane matter. We then observe that the model has a scalar ghost field localized near the brane, as well as quasi-localized massive graviton. Pure tensor structure of four-dimensional gravity on the brane at intermediate distances is due to the cancellation between the extra polarization of the massive graviton, and the ghost. This is completely analogous to the situation in the GRS model.