SNe Ia Redshift in a Nonadiabatic Universe

By relaxing the constraint of adiabatic universe used in most cosmological models, we have shown that the new approach provides a better fit to the supernovae Ia redshift data with a single parameter, the Hubble constant html-italic^>H₀, than the standard ΛCDM model with two parameters, html-italic^>H₀ and the cosmological constant Λ related density, Ω_Λ. The new approach is compliant with the cosmological principle. It yields the html-italic^>H₀ = 68.28 (±0.53) km s⁻¹ Mpc⁻¹ with an analytical value of the deceleration parameter html-italic^>q₀ = −0.4. The analysis presented is for a matter-only, flat universe. The cosmological constant $\Lambda$ may thus be considered as a manifestation of a nonadiabatic universe that is treated as an adiabatic universe.