Cosmic expansion driven by gravitational particle production: toward a complete cosmological scenario

Abstract A dark-energy-free cosmological model $$(\Omega _{DE} \equiv 0)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>Ω</mml:mi> <mml:mrow> <mml:mi>DE</mml:mi> </mml:mrow> </mml:msub> <mml:mo>≡</mml:mo> <mml:mn>0</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> 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 $$(\alpha ,$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>α</mml:mi> <mml:mo>,</mml:mo> </mml:mrow> </mml:math> $$\beta )$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>β</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> , reproduces a $$\Lambda $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>Λ</mml:mi> </mml:math> CDM-like expansion for suitable $$\alpha ,$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>α</mml:mi> <mml:mo>,</mml:mo> </mml:mrow> </mml:math> while $$\beta $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>β</mml:mi> </mml:math> introduces small but testable deviations from the cosmic concordance model. Constraints from type Ia Supernovae (Pantheon+SH0ES) and H ( z ) data indicate $$\beta \simeq 0.13,$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>β</mml:mi> <mml:mo>≃</mml:mo> <mml:mn>0.13</mml:mn> <mml:mo>,</mml:mo> </mml:mrow> </mml:math> suggesting a mild departure from standard cosmology and possible relief of the $$H_0$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>H</mml:mi> <mml:mn>0</mml:mn> </mml:msub> </mml:math> and $$S_8$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>S</mml:mi> <mml:mn>8</mml:mn> </mml:msub> </mml:math> 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.