Interacting ultralight dark matter and dark energy and fits to cosmological data in a field theory approach

TL;DR

This paper introduces a Lagrangian field theory model for dark matter and dark energy, analyzing their interactions and perturbations, and fits the model to various cosmological data to address tensions in Hubble and S8 measurements.

Contribution

It proposes a novel Lagrangian framework for interacting dark matter and dark energy, providing an alternative to the standard $ ext{Lambda CDM}$ model with data-driven parameter constraints.

Findings

Model can alleviate Hubble tension.

Model helps resolve S8 tension.

Constraints on dark matter mass and interaction strengths.

Abstract

The description of dark matter as a pressure-less fluid and of dark energy as a cosmological constant, both minimally coupled to gravity, constitutes the basis of the concordance $\Lambda\text{CDM}$ model. However, the concordance model is based on using equations of motion directly for the fluids with constraints placed on their sources, and lacks an underlying Lagrangian. In this work, we propose a Lagrangian model of two spin zero fields describing dark energy and dark matter with an interaction term between the two along with self-interactions. We study the background evolution of the fields as well as their linear perturbations, suggesting an alternative to $\Lambda$CDM with dark matter and dark energy being fundamental dynamical fields. The parameters of the model are extracted using a Bayesian inference tool based on multiple cosmological data sets which include those of Planck (with lensing), BAO, Pantheon, SH0ES, and WiggleZ. Using these data, we set constraints on the dark matter mass and the interaction strengths. Furthermore, we find that the model is able to alleviate the Hubble tension for some data sets while also resolving the $S_8$ tension.