Structure Formation in Dark Matter Particle Production Cosmology

TL;DR

This paper explores a cosmological model where dark matter particles are created during the universe's evolution, using non-equilibrium thermodynamics, and demonstrates it fits observational data better than the standard Lambda-CDM model.

Contribution

It introduces a dark matter creation model within an open thermodynamic framework and shows improved fit to cosmological and large-scale structure data.

Findings

Better fit to Planck, SNe Ia, BAO, and local H0 measurements than Lambda-CDM.

Improved modeling of large-scale structure formation and growth factors.

Enhanced agreement with linear perturbation data.

Abstract

We investigate a cosmological scenario in which the dark matter particles can be created during the evolution of the Universe. By regarding the Universe as an open thermodynamic system and using non-equilibrium thermodynamics, we examine the mechanism of gravitational particle production. In this setup, we study the large-scale structure (LSS) formation of the Universe in the Newtonian regime of perturbations and derive the equations governing the evolution of the dark matter overdensities. Then, we implement the cosmological data from Planck 2018 CMB measurements, SNe Ia and BAO observations, as well as the Riess et al. (2019) local measurement for $H_0$ to provide some cosmological constraints for the parameters of our model. We see that the best case of our scenario ($\chi_{{\rm tot}}^{2}=3834.40$) fits the observational data better than the baseline $\Lambda$CDM model ($\chi_{{\rm tot}}^{2} = 3838.00$) at the background level. We moreover estimate the growth factor of linear perturbations and show that the best case of our model ($\chi_{f\sigma_{8}}^{2}=39.85$) fits the LSS data significantly better than the $\Lambda$CDM model ($\chi_{f\sigma_{8}}^{2}=45.29$). Consequently, our model also makes a better performance at the level of the linear perturbations compared to the standard cosmological model.