Fitting of supernovae without dark energy

TL;DR

This study analyzes supernova data from Pantheon to explore whether the observed acceleration can be explained without dark energy, considering various alternative models and factors like extinction and supernova evolution.

Contribution

It demonstrates that multiple alternative cosmological models can fit supernova data as well as the standard dark energy model, highlighting degeneracies in interpreting the Hubble diagram.

Findings

Standard model fits well but has degeneracies

Alternative models including static and tired light fit data

Degeneracy prevents definitive conclusion on dark energy presence

Abstract

With data from Pantheon, we have at our disposal a sample of more than a thousand supernovae Ia covering a wide range of redshifts with good precision. Here we make fits to the corresponding Hubble--Lema\^itre diagram with various cosmological models, with intergalactic extinction, evolution of the luminosity of supernovae, and redshift components due to partially non-cosmological factors. The data are well fitted by the standard model to include dark energy, but there is a degeneracy of solutions with several other variables. Therefore, the Hubble--Lema\^itre diagram of SNe Ia cannot be used alone to infer the existence of the accelerated expansion scenario with dark energy. Within this degeneracy, models that give good fits to the data include the following alternative solutions: Einstein--de Sitter with gray extinction $a_V=1.2\times 10^{-4}$ Mpc$^{-1}$; linear Hubble--Lema\^itre law static Euclidean with gray extinction $a_V=0.4\times 10^{-4}$ Mpc$^{-1}$; Static Euclidean with tired light and gray extinction $a_V=2.8\times 10^{-4}$ Mpc$^{-1}$; Einstein--de Sitter with absolute magnitude evolution $\alpha =-0.10$ mag Gyr$^{-1}$; Friedmann model with $\Omega _M=0.07 - 0.29$, $\Omega _\Lambda =0$ and partially non-cosmological tired-light redshifts/blueshift with attenuation/enhancement $|K_i|<2.2\times 10^{-4}$ Mpc$^{-1}$ (although requiring calibration of $M$ incompatible with local SNe measurements).