arXiv subjects

Abha Dev

Publications and source records attributed to Abha Dev.

21 records · Page 2Linked to original sources

arXiv2002

Gravitational lensing constraint on the cosmic equation of state

Recent redshift-distance measurements of Type Ia supernovae (SNe Ia) at cosmological distances suggest that two-third of the energy density of the universe is dominated by dark energy component with an effective negative pressure. This dark energy component is described by the equation of state $p_{x} = w ρ_{x}$ $(w \geq -1)$. We use gravitational lensing statistics to constrain the equation of state of this dark energy. We use $n(Δθ)$, image separation distribution function of lensed quasars, as a tool to probe $w$. We find that for the observed range of $Ω_m \sim 0.2 - 0.4$, $w$ should lie between $-0.8 \leq w \leq -0.4$ in order to have five lensed quasars in a sample of 867 optical quasars. This limit is highly sensitive to lens and Schechter parameters and evolution of galaxies.

astro-ph↗

arXiv2001

Constraints on the Cosmic Equation of State using Gravitational Lensing Statistics with evolving galaxies

In this paper, observational constraints on the cosmic equation of state of dark energy ($p = w ρ$) have been investigated using gravitational lensing statistics. A likelihood analysis of the lens surveys has been carried out to constrain the cosmological parameters $Ω_{m}$ and $w$. Constraints on $Ω_{m}$ and $w$ are obtained in three different models of galaxy evolution: no evolution model (comoving number density of galaxies remain constant), Volmerange and Guiderdoni model and fast merging model. The last two models consider the number evolution of galaxies in addition to the luminosity evolution. The likelihood analysis shows that for the no-evolution case $w \leq -0.04$ and $Ω_{m}\leq 0.90$ at $1σ$ (68% confidence level). Similarly for the Volmerange $&$ Guiderdoni Model the constraints are $w \leq -0.04$ and $Ω_{m} \leq 0.91$ at $1 σ$. In fast merging model the constraint become weaker and it allows almost the entire range of parameters. For the case of constant $Λ$ ($w =-1$), all the models permit $Ω_{m} = 0.3$ with 68% CL which is consistent with the value of $Ω_{m} $ inferred from various other cosmological observations.

astro-ph↗

arXiv2000

Linear Coasting in Cosmology and SNe Ia

A strictly linear evolution of the cosmological expansion scale factor is a characteristic feature in several classes of alternative gravity theories as also in the standard (big-bang) model with specially chosen equations of state of matter. Such an evolution has no free parameters as far as the classical cosmological tests are concerned and should therefore be easily falsifiable. In this article we demonstrate how such models present very good fits to the current supernovae 1a data. We discuss the overall viability of such models.

astro-ph↗