Time-Dependent Vacuum Energy Induced by D-Particle Recoil

TL;DR

This paper explores a cosmological model where D-particle recoil induces a time-dependent vacuum energy that diminishes as 1/t^2, potentially explaining the universe's expansion and aligning with observational data.

Contribution

It introduces a novel framework incorporating D-particle recoil effects into cosmology, resulting in a dynamic vacuum energy that influences universe expansion.

Findings

Vacuum energy relaxes as ~1/t^2 for large t

Universe expands with scale factor R(t) ~ t^2 under this energy

Model is compatible with supernova observational constraints

Abstract

We consider cosmology in the framework of a `material reference system' of D particles, including the effects of quantum recoil induced by closed-string probe particles. We find a time-dependent contribution to the cosmological vacuum energy, which relaxes to zero as $\sim 1/ t^2$ for large times $t$. If this energy density is dominant, the Universe expands with a scale factor $R(t) \sim t^2$. We show that this possibility is compatible with recent observational constraints from high-redshift supernovae, and may also respect other phenomenological bounds on time variation in the vacuum energy imposed by early cosmology.