Gravitational Matter Creation, Multi-fluid Cosmology and Kinetic Theory

TL;DR

This paper develops a relativistic kinetic theory framework for multi-fluid cosmology with gravitationally induced particle creation, showing potential to emulate $ ext{Lambda}$CDM and offering new tests for cosmological tensions.

Contribution

It introduces a kinetic and macroscopic description of multi-fluid cosmology with particle creation, including temperature laws and potential quantum-gravitational treatment, and compares cosmological models with and without photon creation.

Findings

Cosmology driven by cold dark matter and baryons mimics $ ext{Lambda}$CDM.

Adding photon creation breaks the emulation, providing a test for models.

Creation of all components affects CMB results and expansion history, impacting cosmological tensions.

Abstract

A macroscopic and kinetic relativistic description for a decoupled multi-fluid cosmology endowed with gravitationally induced particle production of all components is proposed. The temperature law for each decoupled particle species is also kinetically derived. The present approach points to the possibility of an exact (semi-classical) quantum-gravitational kinetic treatment by incorporating back reaction effects for an arbitrary set of dominant decoupled components. As an illustration we show that a cosmology driven by creation of cold dark matter and baryons (without dark energy) evolves like $\Lambda$CDM. However, the complete physical emulation is broken when photon creation is added to the mixture thereby pointing to a crucial test in the future. The present analysis also open up a new window to investigate the Supernova-CMB tension on the values of $H_0$, as well as the $S_8$ tension since creation of all components changes slightly the CMB results and the expansion history both at early and late times. Finally, it is also argued that cross-correlations between CMB temperature maps and the Sunyaev-Zeldovich effect may provide a crucial and accurate test confronting extended CCDM and $\Lambda$CDM models.