Effects of Inhomogeneity on the Causal Entropic prediction of Lambda

TL;DR

This paper examines how inhomogeneity in the universe affects the causal entropic prediction of the cosmological constant Lambda, highlighting the importance of ensemble considerations and black hole evaporation in the prediction's robustness.

Contribution

It extends the causal entropic principle to inhomogeneous cosmologies, analyzing the impact of entropy production and black hole evaporation on Lambda's prediction.

Findings

Inhomogeneity can significantly alter Lambda predictions.

Black hole evaporation influences entropy calculations.

Ensemble considerations are crucial for accurate predictions.

Abstract

The causal entropic principle aims to predict the unexpectedly small value of the cosmological constant Lambda using a weighting by entropy increase on causal diamonds. The original work assumed a purely isotropic and homogeneous cosmology. But even the level of inhomogeneity observed in our universe forces reconsideration of certain arguments about entropy production. In particular, we must consider an ensemble of causal diamonds associated with one cosmology, and we can no longer immediately discard entropy production in the far future of the universe. Depending on our choices for a probability measure and our treatment of black hole evaporation, the prediction for Lambda may be left intact or dramatically altered.