Brane cosmological solutions in six-dimensional warped flux compactifications

TL;DR

This paper explores cosmological solutions in a six-dimensional warped flux compactification model, revealing a power-law inflationary attractor and analyzing tensor perturbations with a stable Kaluza-Klein spectrum.

Contribution

It constructs exact cosmological solutions in a 6D Einstein-Maxwell-dilaton system and analyzes their stability and perturbations using a higher-dimensional perspective.

Findings

Power-law inflationary solutions identified as late-time attractors

Existence of a zero mode in tensor perturbations

Stable Kaluza-Klein mass spectrum without tachyonic modes

Abstract

We study cosmology on a conical brane in the six-dimensional Einstein-Maxwell-dilaton system, where the extra dimensions are compactified by a magnetic flux. We systematically construct exact cosmological solutions using the fact that the system is equivalently described by (6+n)-dimensional pure Einstein-Maxwell theory via dimensional reduction. In particular, we find a power-law inflationary solution for a general dilatonic coupling. When the dilatonic coupling is given by that of Nishino-Sezgin chiral supergravity, this reduces to the known solution which is not inflating. The power-law solution is shown to be the late-time attractor. We also investigate cosmological tensor perturbations in this model using the (6+n)-dimensional description. We obtain the separable equation of motion and find that there always exist a zero mode, while tachyonic modes are absent in the spectrum. The mass spectrum of Kaluza-Klein modes is obtained numerically.