Speaker
Description
The cosmological background and perturbation dynamics have been explored using an interacting dark-fluid model, where energy is exchanged between dark matter and dark energy via diffusion. After solving the background expansion history for the late-time Universe, we aim to constrain the best-fit cosmological parameters ({\Omega_m, h, r_d, Q_m}) through the MCMC simulations using several datasets: Hubble parameter (H(z)) from cosmic chronometers (CC), Baryon Acoustic Oscillations from the Dark Energy Spectroscopic Instrument (DESI), and SNIa distance moduli from the Pantheon+ sample. Joint analyses such as CC+DESI, CC+SNIa, DESI+SNIa, and CC+SNIa+DESI are accompanied by a detailed statistical analysis. With the best-fit values, we provide numerical results for (H(z)), the deceleration parameter (q(z)), the effective equation of state (w_{eff}), and distance moduli (\mu(z)) as functions of redshift to evaluate the dark fluid model's viability in describing cosmic dynamics. Additionally, we analyze diagnostic parameters jerk (r) vs snap (s) and (r) vs (q) to distinguish the dark fluid model's effects, which reveal energy transfer between dark matter and dark energy. The results show that the dark fluid behaves like Chaplygin gas that supports the cosmic acceleration when (Q_m) is negative and exhibits a quintessence phase when (Q_m) is positive. This work also aims to derive the evolution equation of the matter density contrast (\delta(z)) using $1+3$ covariant formalism, present the numerical results of $\delta(z)$, and demonstrate the growth rate $f(z)$ and the redshift space distortion using the large-scale structure datasets. The best fit values of the corresponding parameters {(\Omega_m,\sigma_8, Q_m)} with detailed statistical analysis.
| Abstract Category | Astrophysics & Cosmology |
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