https://doi.org/10.1140/epjc/s10052-024-12667-z
Regular Article - Theoretical Physics
On redshift evolution and negative dark energy density in Pantheon + Supernovae
1
Department of Physics, Bu-Ali Sina University, 65178, Hamedan, Iran
2
Atlantic Technological University, Ash Lane, Sligo, Ireland
3
School of Physics, Institute for Research in Fundamental Sciences (IPM), P.O.Box 19395-5531, Tehran, Iran
Received:
17
November
2023
Accepted:
10
March
2024
Published online:
25
March
2024
Within the Friedmann–Lemaître–Robertson–Walker (FLRW) framework, the Hubble constant is an integration constant. Thus, consistency of the model demands observational constancy of
. We demonstrate redshift evolution of best fit
CDM parameters
in Pantheon+ supernove (SNe). Redshift evolution of best fit cosmological parameters is a prerequisite to finding a statistically significant evolution as well as identifying alternative models that are competitive with
CDM in a Bayesian model comparison. To assess statistical significance, we employ three different methods: (i) Bayesian model comparison, (ii) mock simulations and (iii) profile distributions. The first shows a marginal preference for the vanilla
CDM model over an ad hoc model with 3 additional parameters and an unphysical jump in cosmological parameters at
. From mock simulations, we estimate the statistical significance of redshift evolution of best fit parameters and negative dark energy density (
) to be in the
range, depending on the criteria employed. Importantly, in direct comparison to the same analysis with the earlier Pantheon sample we find that statistical significance of redshift evolution of best fit parameters has increased, as expected for a physical effect. Our profile distribution analysis demonstrates a shift in
in excess of
confidence level for SNe with redshifts
and also shows that a degeneracy in MCMC posteriors is not equivalent to a curve of constant
. Our findings can be interpreted as a statistical fluctuation or unexplored systematics in Pantheon+ or
CDM model breakdown. The first two possibilities are disfavoured by similar trends in independent probes.
© The Author(s) 2024
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