Abstract

This study examines the gravitational and thermodynamic properties of static, spherically symmetric black holes within cosmic voids - vast underdense regions of the universe. By deriving a novel solution based on a universal density profile for voids, we analyze its spacetime structure, which reveals two horizons: one of the black hole and the other related to the de Sitter-like behavior. As the void approaches a perfect vacuum, the black hole horizon diminishes, tending to that of the Schwarzschild solution, while the outer horizon increases. We also study the solution stability via sound speed of the fluid, as well as the thermodynamic properties, including Hawking temperature, evaporation time, entropy, and specific heat. Our results show that as the void empties, the Hawking temperature rises, shortening evaporation times. The entropy follows the area's law and specific heat exhibits a minimum for a given black hole size, indicating a thermal transition and highlighting the role of voids in the black hole evolution. These findings offer new insights into the relationship between local gravitational collapse and large-scale cosmic structure, enhancing our understanding of the black hole behavior in underdense environments. We also provide a glimpse of a potential thermodynamic interaction between the event horizon and the cosmological horizon.