arXiv subjects

Savita Gahlaut

Publications and source records attributed to Savita Gahlaut.

4 recordsLinked to original sources

arXiv2026

Investigating the coincidence problem with Interacting Dark Energy Models

Interacting dark energy (IDE) models within the framework of general relativity (GR) provide a possible extension of the standard $Λ$CDM model and may alleviate the coincidence problem. In this paper, we investigate three phenomenological interacting dark energy models using a combination of cosmic chronometer $H(z)$ measurements and two standard cosmic rulers: baryon acoustic oscillations (BAO) and quasars (QSO). The observational constraints indicate a mild preference for energy transfer from dark energy to dark matter, a scenario that may help alleviate the cosmic coincidence problem. However, the standard $Λ$CDM model, corresponding to the absence of interaction, remains fully consistent with the observational data, as the no-interaction case lies within the $1σ$ confidence interval of the inferred interaction parameter for all three IDE models. Model comparison, using Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC), further indicates that the current data do not provide statistically significant evidence favouring any IDE model over the standard $Λ$CDM scenario or over one another. These results suggest that, while a weak dark-sector interaction is permitted by the data, present observations do not provide compelling evidence for departures from the standard $Λ$CDM model.

physics.gen-ph↗

arXiv2026

Model Independent Probe of Variation of Cosmic Opacity with Redshift

Cosmic opacity may vary spatially due to the inhomogeneous distribution of dust, its grain properties, and the efficiency of photon attenuation. In this work, we present a model independent method to investigate the variation of cosmic opacity with redshift. Using strong gravitational lensing data we construct the opacity independent comoving distance function and we use latest supernovae type Ia (SNe Ia) Pantheon+ data to estimate the opacity dependent comoving distances. Using the distance duality equation, opacity parameter is constrained. Our analysis indicates a transparent Universe on average over the redshift range ($0.01 \leq z \leq 2.26137$) of Pantheon+ sample. However, if we split the dataset into subsamples with redshift bins of width $\bigtriangleup z = 0.1$, we find appreciable deviation from the transparency in several redshift intervals. Particularly, in the redshift range $0.3 < z \leq 0.4$, the opacity parameter is $ε= -0.4283^{+0.1914}_{-0.2027}$. The current SNe Ia observations indicate the variation of opacity parameter with redshift. These results may have a significant impact on the values of the cosmological parameters deduced from the SNe Ia observations.

astro-ph.CO↗

arXiv2025

Model-Independent Probe of Cosmic Distance Duality Relation

In this paper, cosmic distance duality relation is probed without considering any background cosmological model. The only \textit{a priori} assumption is that the Universe is described by the Friedmann-Lema$\hat{i}$tre-Robertson-Walker (FLRW) metric The strong gravitational lensing (SGL) data is used to construct the dimensionless co-moving distance function $d(z)$ and latest type Ia supernovae (SNe Ia) Pantheon+ data is used to estimate luminosity distances at the corresponding redshifts $z$. Using the distance sum rule along null geodesics of the FLRW metric, the CDDR violation is probed in both flat and non-flat space-time by considering two parametrizations for $η(z)$, the function generally used to probe the possible deviations from CDDR. The results show that, CDDR is compatible with the observations at a very high level of confidence for linear parametrization in flat Universe. In non-flat Universe too, CDDR is valid within $1σ$ confidence interval with a mild dependence of $η$ on the curvature density parameter $Ω_{K}$ . The results for non-linear parametrization also show no significant deviation from CDDR.

gr-qc↗

arXiv2024

Testing Linearly Coasting Cosmology by Strong Lensing System and Pantheon+ Data

The standard model of cosmology ($Λ$CDM) is facing a serious crisis caused by the inconsistencies in the measurements of some fundamental cosmological parameters (Hubble constant $H_{0}$ and cosmic curvature parameter $Ω_{k}$ for example). On the other hand, a strictly linear evolution of the cosmological scale factor is found to be an excellent fit to a host of observations. Any model that can support such a coasting presents itself as a falsifiable model as far as the cosmological tests are concerned. In this article the observational data of strong gravitational lensing (SGL) systems from SLACS, BELLS, LSD and SL2S surveys has been used to test the viability of linearly coasting cosmology. Assuming the spherically symmetric mass distribution in lensing galaxies, the ratio of angular diameter distance from lens to source and angular diameter distance of the source is evaluated and is used to constrain the power law cosmology. Further, updated type Ia supernovae dataset (Pantheon+) with covariance matrix incorporating all statistical and systematic uncertainties is used to constrain the power law cosmology. It is found that the linear coasting is consistent with the SGL data within 1-$σ$ uncertainties but Pantheon+ sample does not support linear coasting.

astro-ph.CO↗