Is dark energy an effective manifestation of non-equilibrium thermodynamics? – insights from DESI

Abstract We investigate the background cosmological expansion on the onset of cosmological homogeneous matter creation scenario, a dynamical dark matter approach ( w dm ≠ 0 ), and an alternative approach to both dark energy and modified gravity theories, after the recent dark energy spectroscopic instrument (DESI) DR2-Baryon acoustic oscillations (BAO) release. We consider that the total matter sector consists of three independently evolving components, namely, radiation, baryons, and dark matter, with the latter being governed by an adiabatic matter creation process, affects the background homogeneously, leads to a modified continuity equation. Though the total stress–energy tensor is conserved the only violation of the conservation law in the dark matter sector is coming from the creation pressure, and under a proper choice of dark-matter particle creation rate one can obtain the present accelerating phase as well as the past thermal history of the Universe. We study two specific matter creation rates. By applying the dynamical-system analysis we show that both Model I and Model II can mimic a Λ -cold dark matter ( Λ CDM)-like behavior. Furthermore,we perform a detailed observational confrontation using a series of latest observational datasets including cosmic chronometers, Supernovae Type Ia (Pantheon+, DESY5 and Union3 samples) and DESI BAO (DR1 and DR2 samples). In both Model I and Model II we find evidence of matter creation at many standard deviations. Finally, applying the Akaike information criterion and Bayesian information criterion information criteria we find that Model I is statistically equivalent with Λ CDM scenario, while Model II shows a mixed picture, namely for most datasets Λ CDM scenario is favoured, however when DESI data are includedmatter creation Model II is favored over Λ CDM paradigm.