http://arxiv.org/abs/2205.13247
One of the most significant discoveries in modern cosmology is that the universe is currently in a phase of accelerated expansion after a switch from a decelerated expansion. The precise determination of the time of this transition from a decelerated phase to an accelerated phase has been a topic of wide interest. This redshift is commonly referred to as the transition redshift $z_t$. This paper aims to put constraints on the transition redshift with both model-dependent and model-independent approaches. We divide this paper into two parts. In first part we follow a model dependent approach. Here, we consider a non-flat $\Lambda$CDM model as a background cosmological model and use the Hubble parameter measurements of 33 datapoints to construct the cosmic triangle. Further we reconstruct another cosmic triangle plot between $\log(\Omega_{m0})$, $-\log(2\Omega_{\Lambda0})$ and $3\log(1+z_t)$ where the constraints of each parameter are determined by the location in this triangle plot. Using $\Omega_{m0}$ and $\Omega_{\Lambda0}$ values, we find the best value of transition redshift $z_t=0.623^{+0.567}{-0.783}$, which is in good agreement with the Planck 2018 results at $1\sigma$ confidence level. The second part is based on a non-parametric method. We plot a Hubble Phase Space Portrait (HPSP) between $\dot{H}(z)$ and $H(z)$. From this HPSP diagram, we estimate the transition redshift as well as the current value of equation of state parameter $\omega_0$ in a model-independent way. We find the best fit value of $z_t=0.601^{+0.313}{-0.313}$ and $\omega_0=-0.654^{+0.258}_{-0.258}$. We also simulate the observed Hubble parameter measurements in the redshift range $0<z<2$ and perform the same analysis to estimate the transition redshift.
D. Kumar, D. Jain, S. Mahajan, et. al.
Fri, 27 May 22
6/61
Comments: 10 Pages, 9 Figures, 3 Tables. Comments welcome!