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

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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.