Pseudo-3-Branes in a Curved 6D Bulk

TL;DR

This paper explores a 6D brane-world model with sigma fields and an axion that cancels pressure, leading to a potential solution to the cosmological constant problem, and discusses gravity with brane sources.

Contribution

It introduces a 6D brane model with an axion field that cancels pressure, resulting in a non-compact transverse space and addressing the cosmological constant problem.

Findings

Non-compact transverse space can solve the cosmological constant problem.

A mild fine-tuning is required for compact two-brane setups.

Analysis of gravity in the presence of branes using Gauss-Codazzi formulation.

Abstract

We consider a model involving a 4-brane in a 6D bulk which carries sigma model fields. An axion field on the 4-brane cancels the pressure along one direction leading to an effective codimension-2 3-brane. For a range of parameters of the theory, we get a transverse space which is non-compact, providing a possible solution to the cosmological constant problem. A setup with two branes in a compact space is also treated. In this case, a mild fine-tuning between the radii of the two 4-branes is necessary. Finally, we explore the 4-brane problem in the Gauss-Codazzi formulation and we discuss general aspects of gravity in the presence of additional brane sources.