Codimension Two Compactifications and the Cosmological Constant Problem

TL;DR

This paper explores six-dimensional models with two compact dimensions, demonstrating that brane tensions do not affect the four-dimensional cosmological constant, which can be tuned independently of brane tensions, addressing aspects of the cosmological constant problem.

Contribution

It introduces a class of six-dimensional solutions where the four-dimensional cosmological constant is independent of brane tensions, avoiding fine-tuning of these tensions.

Findings

Effective 4D cosmological constant is independent of brane tensions.

Arbitrary brane tensions do not require fine tuning.

Bulk parameters must be fine-tuned for small observable cosmological constant.

Abstract

We consider solutions of six dimensional Einstein equations with two compact dimensions. It is shown that one can introduce 3-branes in this background in such a way that the effective four dimensional cosmological constant is completely independent of the brane tensions. These tensions are completely arbitrary, without requiring any fine tuning. We must, however, fine tune bulk parameters in order to obtain a sufficiently small value for the observable cosmological constant. We comment in the effective four dimensional description of this effect at energies below the compactification scale.