Higher-dimensional perturbations of the vacuum energy density

TL;DR

This paper investigates how supersymmetry breaking in higher-dimensional models affects vacuum energy transfer between a brane and bulk, revealing bounds on the SUSY scale to align with cosmological constraints.

Contribution

It demonstrates that residual vacuum energy from supersymmetry breaking cannot be fully off-loaded to the bulk and establishes bounds on the SUSY scale based on backreaction effects.

Findings

Residual energy transfer back to the brane constrains SUSY scale.

The effect is independent of the number of extra dimensions.

Zero-point energies of higher-dimensional states are computed.

Abstract

The vacuum energy density arising from the broken supersymmetry of the (standard-model) fields living on a brane cannot be fully "off-loaded" to the bulk: even assuming the existence of an effective "self-tuning" mechanism, a small fraction of the transferred energy "bunces back" to the brane, as a backreaction of the supersymmetry breaking gravitationally transmitted to the bulk. In that case the SUSY scale of the brane has to be bounded, to guarantee the consistency of such a residual energy density with current large-scale phenomonological constraints. This effect is illustrated by computing the zero-point energies of the tower of (higher-dimensional) massive states associated to tensor metric fluctuations on a brane embedded in a warped bulk geometry, and it is shown to be independent of the number of compact or non-compact extra dimensions.