Micrometer Gravitinos and the Cosmological Constant

TL;DR

This paper calculates the cosmological constant in string compactifications with a non-supersymmetric brane and a supersymmetric bulk, predicting tiny values consistent with observations and new superpartners of the graviton.

Contribution

It introduces a model where the cosmological constant arises solely from bulk supergravity vacuum energy, linking TeV-scale brane supersymmetry breaking to a micrometer-scale bulk breaking.

Findings

Cosmological constant matches observed tiny value.

Predicts superpartners of the graviton at ~10^{-3} eV.

Suggests observable effects in short-distance gravity tests.

Abstract

We compute the 4--dimensional cosmological constant in string compactifications in which the Standard Model fields live on a non-supersymmetric brane inside a supersymmetric bulk. The cosmological constant receives contributions only from the vacuum energy of the bulk supergravity fields, but not from the vacuum energy of the brane fields. The latter is absorbed in a warp factor. Supersymmetry breaking on the brane at the TeV scale implies supersymmetry breaking in the bulk at the micrometer scale. This produces a tiny cosmological constant that agrees with experiment within a few orders of magnitude. Our argument predicts superpartners of the graviton with mass of order $10^{-3}$ eV. They should be observable in short-distance tests of Einstein Gravity.