A Breathing Mode for Warped Compactifications

TL;DR

This paper introduces the warped breathing mode, a gauge-invariant fluctuation mode in warped compactifications that combines the volume modulus and dilaton, affecting the understanding of degrees of freedom in flux compactifications.

Contribution

It identifies and characterizes the warped breathing mode as a new gauge-invariant degree of freedom in warped compactifications, valid for all warping strengths.

Findings

The warped breathing mode exists as a zero mode deformation.

It combines the volume modulus and dilaton into a single gauge-invariant mode.

Impacts the interpretation of degrees of freedom in flux compactifications.

Abstract

In general warped compactifications, non-trivial backgrounds for the warp factor and the dilaton break $D$-dimensional diffeomorphism invariance, so that dilaton fluctuations can be gauged away completely and eaten by the metric. More specifically, the warped volume modulus and the dilaton are not independent, but combine into a single gauge-invariant degree of freedom in the lower dimensional effective theory, the warped breathing mode. This occurs for all strengths of the warping, even the weakly warped limit. This warped breathing mode appears as a natural zero mode deformation of backgrounds sourced by p-branes, and affects the identification of the independent degrees of freedom of flux compactifications.