Evidence for Dynamical Dark Energy using DESI DR2 Ly$α$ Forest
Authors
Salvatore Capozziello
Himanshu Chaudhary
G. Mustafa
S. K. J. Pacif
Abstract
We present a comprehensive analysis of the cosmological implications of the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) Lyman-$α$ forest baryon acoustic oscillation (BAO) measurements, combined with complementary datasets DESI DR2 galaxy BAO, Type Ia supernova (Pantheon$^+$, DES-SN5Y, and Union3), and compressed CMB likelihood. We test several dynamical dark energy models CPL, logarithmic, exponential, JBP, BA, and GEDE as well as $ω$CDM and non-flat extensions of the standard $Λ$CDM and $ω$CDM models. Using the Metropolis Hastings MCMC algorithm implemented in \texttt{SimpleMC}, we constrain the cosmological parameters of each model and evaluate the Bayesian evidence using \texttt{MCEvidence} to assess each model's performance relative to $Λ$CDM. Our results show that the inclusion of DESI DR2 Ly$α$ data modestly enhances sensitivity to departures from $Λ$CDM. Our results show non-flat extensions remain consistent with spatial flatness ($Ω_k \approx 0$ within $1$-$2σ$). Further, all redshift dependent dark energy models predict $ω_0 > -1$, $ω_a < 0$, and $ω_0 + ω_a < -1$, favor a dynamical dark energy scenario characterized by Quintom-B type, and we found that dynamical dark energy favors over the $Λ$CDM model ranging from 0.24-2.60$σ$, depending on the choice of model and corresponding combination of datasets. Bayesian evidence comparison favors the $ω$CDM model with moderate evidence over $Λ$CDM, whereas other parameterizations remain statistically inconclusive.
