On the thin-string limit of the 6d stringlike defect model

TL;DR

This paper demonstrates that in 6d stringlike defect models satisfying energy conditions, the exterior metric depends on the string's thickness, leading to gravity delocalization or a large Planck scale discrepancy in the thin-string limit.

Contribution

It reveals the fundamental limitation of thin-string approximations in 6d models with localized gravity under energy conditions.

Findings

Exterior metric depends on string thickness

Thin-string limit causes gravity delocalization

Large discrepancy between 6d and 4d Planck scales

Abstract

We show that in 6d models localizing gravity on stringlike defects and satisfying the dominant energy condition, the metric exterior to the string inevitably depends on the string's thickness. As a consequence, in the limit of thin string either the gravity delocalizes, or the six-dimensional Planck scale must be much larger that the four-dimensional one.