Cosmic Expansion Driven by Gravitational Particle Production: Toward a Complete Cosmological Scenario

Abstract

A dark-energy-free cosmological model ($\Omega_{DE} \equiv 0$) based on gravitationally induced adiabatic particle creation is proposed. The thermodynamics of particle production yields an effective negative pressure that drives both primordial inflation and late-time cosmic acceleration. The model, characterized by four components and two free parameters ($\alpha$, $\beta$), reproduces a $\Lambda$CDM-like expansion for suitable $\alpha$, while $\beta$ introduces small but testable deviations from the cosmic concordance model. Constraints from type Ia Supernovae (Pantheon+SH0ES) and H(z) data indicate $\beta \simeq 0.13$, suggesting a mild departure from standard cosmology and possible relief of the $H_0$ and $S_8$ tensions. The resulting classical cosmology evolves smoothly between two extreme de Sitter phases, offering a singularity-free, unified scenario that beyond solving old cosmological puzzles opens a new perspective to handle the tensions plaguing the current cosmic concordance model.