Saltatory Relaxation of the Cosmological Constant

TL;DR

This paper proposes a modified mechanism involving brane nucleation and string theory insights to dynamically relax the cosmological constant, linking it to supersymmetry breaking and universe stability.

Contribution

It introduces two key innovations from string theory to the relaxation framework, affecting the dynamics and quantization of the cosmological constant.

Findings

Small quantized jumps in the cosmological term are generated by extra-dimensional compactification.

Enhanced tunneling rates arise from internal degrees of freedom of multiply coincident branes.

A relation between supersymmetry breaking scale and the cosmological constant is derived.

Abstract

We modify and extend an earlier proposal by Brown and Teitelboim to relax the effective cosmological term by nucleation of branes coupled to a three-index gauge potential. Microscopic considerations from string/M theory suggest two major innovations in the framework. First, the dependence of brane properties on the compactification of extra dimensions may generate a very small quantized unit for jumps in the effective cosmological term. Second, internal degrees of freedom for multiply coincident branes may enhance tunneling rates by exponentially large density of states factors. These new features essentially alter the relaxation dynamics. By requiring stability on the scale of the lifetime of the universe, rather than absolute stability, we derive a non-trivial relation between the supersymmetry breaking scale and the value of the cosmological term. It is plausibly, though not certainly, satisfied in Nature.