Dark Interactions and Cosmological Fine-Tuning

TL;DR

This paper investigates whether models with dark matter and dark energy interactions can address the coincidence and smallness problems in cosmology, analyzing their observational viability and theoretical potential.

Contribution

It introduces a general coupling scheme to unify various dark interaction models and assesses their effectiveness in solving key cosmological fine-tuning issues.

Findings

Models can potentially alleviate the coincidence problem.

Observational data constrains the strength of dark interactions.

Theoretical analysis suggests limited capacity to fully resolve fine-tuning issues.

Abstract

Cosmological models involving an interaction between dark matter and dark energy have been proposed in order to solve the so-called coincidence problem. Different forms of coupling have been studied, but there have been claims that observational data seem to narrow (some of) them down to something annoyingly close to the $\Lambda$CDM model, thus greatly reducing their ability to deal with the problem in the first place. The smallness problem of the initial energy density of dark energy has also been a target of cosmological models in recent years. Making use of a moderately general coupling scheme, this paper aims to unite these different approaches and shed some light as to whether this class of models has any true perspective in suppressing the aforementioned issues that plague our current understanding of the universe, in a quantitative and unambiguous way.