A Strong Constraint on Ever-Present Lambda

TL;DR

This paper demonstrates that the causal set approach to a persistent cosmological constant is limited by cosmic microwave background isotropy and observational data, making it unlikely to explain late-time universe acceleration.

Contribution

It provides constraints on the causal set model of a constant lambda, showing it cannot account for observed cosmic acceleration due to small fluctuations.

Findings

Fluctuations are too small to influence expansion at z<1000

The model is only viable in 3+1 dimensions

Observational data strongly constrains the model

Abstract

We show that the causal set approach to creating an ever-present cosmological 'constant' in the expanding universe is strongly constrained by the isotropy of the microwave background. Fluctuations generated by stochastic lambda generation which are consistent with COBE and WMAP observations are far too small to dominate the expansion dynamics at z<1000 and so cannot explain the observed late-time acceleration of the universe. We also discuss other observational constraints from the power spectrum of galaxy clustering and show that the theoretical possibility of ever-present lambda arises only in 3+1 dimensional space-times.