The Horizon of the McVittie Black Hole: On the Role of the Cosmic Fluid Modeling

TL;DR

This study explores how different complex cosmic fluids influence the evolution of cosmological and event horizons in a McVittie universe, revealing the impact of fluid interactions on horizon dynamics and black hole physics.

Contribution

It introduces a detailed analysis of horizon evolution in a McVittie universe driven by various non-ideal fluids, highlighting the role of fluid interactions and conditions for horizon existence.

Findings

Cosmological horizon expands over time.

Event horizon shrinks over time.

Fluid interactions significantly affect event horizon evolution.

Abstract

In this paper, we investigate the existence and time evolution of the cosmological and event horizons in a McVittie universe whose expansion is driven by the Redlich-Kwong, (Modified) Berthelot, Dieterici, and Peng-Robinson fluids, respectively. The equations of state of these fluids are rich enough to account for both exotic and regular, as well as ideal and non-ideal matter contents of the universe. We show that the cosmological horizon is expanding, while the event horizon is shrinking along the cosmic time evolution. The former achieves larger size for regular types of matter, contrary to the latter. The strength of interactions within the cosmic fluid are shown to play a more important role in affecting the evolution of the event horizon, rather than of the cosmological horizon in the case of a singularity-free universe. While the cosmological horizon always exists during the time evolution, the event horizon can exist only when a certain relationship between the Hawking-Hayward quasi-local mass and the Hubble function is fulfilled. In this manner, we can study the role played by the large-scale physics (cosmic evolution) on the local scale physics (evolution of a black hole).