Singular Behavior of the Dark Universe under the Effect of Thermal Radiation in Curved Spacetime

We consider the late-time accelerated universe in the Friedmann-Robertson-Walker (FRW) spacetime with a nonzero curvature, and investigate cosmological models when the cosmic fluid is taken to be inhomogeneous and viscous (bulk viscous), coupled to dark matter. We consider the influence from thermal effects caused by Hawking radiation on the formation of singularities of various classified types, within a finite time. It is shown that under the influence of Hawking radiation, the time of formulation of a singularity and the nature of the singularity itself can change. It is also shown that by jointly taking into account radiation, viscosity, and space curvature, one can obtain a singularity-free universe. The symmetry properties of this kind of theory lie in the assumption about spatial isotropy. The spatial isotropy is also reflected in our use of a bulk instead of a shear viscosity.

Automated summary

This article investigates the late-time accelerated universe with non-zero curvature in the FRW spacetime, considering an inhomogeneous and viscous (bulk viscous) cosmic fluid coupled with dark matter. The influence of thermal effects caused by Hawking radiation on the formation of various types of singularities within a finite time is explored. It is found that the presence of Hawking radiation can alter the time of singularity formation and the nature of the singularity itself. Additionally, the combined effects of radiation, viscosity, and space curvature result in a singularity-free universe. The assumption of spatial isotropy is crucial in this theory, which is reflected in the use of bulk viscosity instead of shear viscosity.