Galaxy Formation Efficiency and the Multiverse Explanation of the Cosmological Constant with EAGLE Simulations

TL;DR

This study uses EAGLE simulations to examine how varying the cosmological constant affects galaxy and star formation, finding its influence is subtle and depends on the measure used in multiverse models.

Contribution

It demonstrates that changes in the cosmological constant have limited impact on galaxy formation, challenging explanations of its value based solely on structure formation.

Findings

Star formation rate peaks before acceleration begins

Variations in Lambda have minor effects on star formation efficiency

The observed Lambda value depends on the multiverse measure

Abstract

Models of the very early universe, including inflationary models, are argued to produce varying universe domains with different values of fundamental constants and cosmic parameters. Using the cosmological hydrodynamical simulation code from the eagle collaboration, we investigate the effect of the cosmological constant on the formation of galaxies and stars. We simulate universes with values of the cosmological constant ranging from Lambda = 0 to Lambda_0 = 300, where Lambda_0 is the value of the cosmological constant in our Universe. Because the global star formation rate in our Universe peaks at t = 3.5 Gyr, before the onset of accelerating expansion, increases in Lambda of even an order of magnitude have only a small effect on the star formation history and efficiency of the universe. We use our simulations to predict the observed value of the cosmological constant, given a measure of the multiverse. Whether the cosmological constant is successfully predicted depends crucially on the measure. The impact of the cosmological constant on the formation of structure in the universe does not seem to be a sharp enough function of Lambda to explain its observed value alone.