Metastable gravity on classical defects

TL;DR

This paper explores how metastable gravity can be realized on classical defects in infinite-volume extra dimensions, highlighting the conditions needed and differences across defect codimensions.

Contribution

It provides a detailed analysis of conditions for metastable gravity on defects, especially for codimension greater than two, without necessarily violating energy conditions.

Findings

Metastable gravity requires violation of energy conditions for codimension 2 defects.

Higher codimension defects can support metastable gravity without energy condition violations.

Detailed analysis of a six-dimensional hyperstring model illustrates these conditions.

Abstract

We discuss the realization of metastable gravity on classical defects in infinite-volume extra dimensions. In dilatonic Einstein gravity, it is found that the existence of metastable gravity on the defect core requires violation of the Dominant Energy Condition for codimension Nc = 2 defects. This is illustrated with a detailed analysis of a six-dimensional hyperstring minimally coupled to dilaton gravity. We present the general conditions under which a codimension Nc > 2 defect admits metastable modes, and find that they differ from lower codimensional models in that, under certain conditions, they do not require violation of energy conditions to support quasi-localized gravity.