Constraining Bianchi type I universe with type Ia supernova and H(z) data

Abstract

We use recent 36 observational Hubble data (OHD) in the redshift range .07 ≤ z ≤ 2.36, the joint light curves (JLA) sample, comprised of 740 type Ia supernovae (SNIa) in the redshift range 0.01 ≤ z ≤ 1.30, and their joint combination datasets to constrain anisotropic Bianchi type I (BI) dark energy model(DE). To estimate model parameters, we used Metropolis-Hasting algorithm to perform Monte Carlo Markov Chain analysis. We also compute the covariant matrix for BI dark energy model considering different datasets to compare the correlation between parameters of the model. To check the acceptability of our fittings, all results are compared with those obtained from 9 year WMAP as well as Planck (2015) collaboration. Our estimations show that at 68% confidence level, the dark energy equation of state (EOS) parameter for JLA data varies in quintessence-phantom region while for OHD and the joint combination of datasets only varies in phantom region. It is found that the current cosmic anisotropy is of order ∼ 10 −3 which imply that OHD and JLA datasets do not put tight constrain on this parameter. The deceleration parameter is obtained as q = −0.46 +0.89+0.36 −0.41−0.37 , q = −0.619 +0.12+0.20 −0.0.095−0.24 , and q = −0.52 +0.080+0.014 −0.046−0.15 for H(z), SNIa, and H(z)+SNIa data respectively.

Cosmological viscous fluid models describing infinite time singularities in f(T) gravity

“…In the left panel, one sees that with interaction parameter, the EoS of both non-viscous and viscous dark energy approach the cosmological constant region (W DEe f f = −1) for low values of redshift. But in the panel at the right handside, the EoS parameter has the same behavior as the one in [53] because a comparative analysis of these both panels shows that the parameter W DEe f f of non-viscous dark energy [39], where the interaction alleviates the EoS parameter of dark energy from phantom region (for high redshift) to quintessence region (for low redshift) that evolves to the phantom region.…”

“…In the following, the dark matter will be assumed to be a dust, so ω m = 0. We will also consider in the first party of this work, the general form of bulk viscosity as [53]…”

“…The We can see that these both EoS parameters evolve in quintessence phase, then in f (T ) gravity, universe is in accelerated expansion phase with high and low redshift. In [53], the EoS parameter for viscous Dark Energy varies in unstable phantom region and there is a transition from phantom to the cosmological constant phase at late time. In f (R) modified gravity [39], as we approach null redshift, universe seems to enter phantom phase.…”

“…In order to ensure that the second law of thermodynamics is fulfilled, the interaction parameter Q must be positive [50][51][52]. In the same way like [53], one writes the interaction parameter in the form:…”

“…At the end of this section, we will explore a second example of cosmological model where the Hubble parameter is given by [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56]:…”