Speaker
Description
Under the assumption of thermal equilibrium between the horizon and the fluid inside, we conducted a thermodynamic stability analysis on a model designed to mimic the characteristics of the $\Lambda$CDM model, which is the prevailing framework for portraying the cosmic acceleration. The scale factor for this model is defined as $a\sim \sinh^{2/3}(t/t_0)$. The Hayward-Kodama temperature is opted for the evolving apparent horizon. The outcome of this analysis yielded a remarkable finding: the thermal capacity exhibited a negative value and a lack of thermodynamic stability within the cosmic matter enclosed by the horizon.
The significance of this study lies in the result indicating that the matter content experiences a phase transition precisely at the value of $z$ where the Universe undergoes a transition from decelerated expansion to an accelerated one. Notably, this phase transition manifests characteristics akin to those of a second-order phase transition, as indicated by the discontinuity in heat capacity at constant volume ($C_V$). The deceleration parameter ($q$) serves as the order parameter and solidifies this correlation.
| td14ip021@iiserkol.ac.in | |
| Affiliation | INDIAN INSTITUTE OF SCIENCE EDUCATION AND RESEARCH KOLKATA(IISER Kolkata) |
