Dynamical dark energy signatures from a new transition Om(z) parametrization in flat FLRW cosmology
Year: 2026
Type: article
Abstract: We investigate a cosmic scenario using a new transition parameterization of the $Om(z)$ diagnostic, $Om(z) = \frac{z^l}{(1+z)^m}$, in the spatially flat Friedmann Lemaître Robertson-Walker (FLRW) framework. Using observational datasets such as Observational Hubble Data (OHD), Pantheon Plus (PP), and SH0ES, we analyze the evolution of the $Om(z)$ function to probe deviations from the standard $\Lambda$CDM model and constrain free parameter space {$H_0$, l, m } using Markov Chain Monte Carlo (MCMC) analysis with the emcee sampler. Our analysis reveals a clear transition in the slope of $Om(z)$ from negative to positive at transition redshift values $z_t \approx 1.41$, $0.65$, and $0.33$ for the OHD, OHD+PP, and OHD+PP+SH0ES datasets, respectively. This behavior suggests a dynamical evolution of dark energy, indicating a transition from a quintessence-like phase to a phantom regime. From the combined OHD+PP+SH0ES dataset, we obtain a best-fit value of the Hubble constant \( H_0 = 73.01 \pm 0.36 \, \mathrm{km\,s^{-1}\,Mpc^{-1}} \), which is consistent with the SH0ES calibration and supports the viability of our model. Furthermore, our analysis constrains the Universe's current age lies around $13 \sim 14$ Gyr from all given combinations of datasets, consistent with observational expectations, and also finds that the deceleration-to-acceleration transition, marking the onset of cosmic acceleration, is inferred to occur within the redshift interval $z_t \in [0.5, 0.8]$, underscoring the emergence of dark energy as the dominant component in the Universe’s recent expansion history. Our transition $Om(z)$ parameterization captures progressive cosmological changes and enables seamless interpolation over cosmic epochs.
Source: Physics Letters B
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W7127065634