Thermodynamics and Microscopic Structure of Black Holes

Black hole thermodynamics has emerged as a pivotal framework for bridging gravitational dynamics with quantum statistical mechanics, suggesting deep connections between classical space time geometry and microscopic degrees of freedom. This work presents a comprehensive analysis of the thermodynamic behavior of black holes, emphasizing the roles of Hawking radiation, entropy–area relations, and phase transitions in various gravity theories. Starting from the foundational laws of black hole thermodynamics, we review how temperature and entropy are defined in terms of surface gravity and horizon area, respectively, and explore corrections arising from quantum effects and higher-curvature terms. A central focus is the investigation of candidate microscopic models that account for black hole entropy, including string theory microstates, loop quantum gravity spin networks, and holographic entanglement structures in the context of the AdS/CFT correspondence. We analyze how these frameworks yield statistical interpretations of entropy and address the information paradox through microscopic state counting. Furthermore, we discuss recent developments in black hole phase structure, such as Van der Waals–like behavior in extended phase spaces where the cosmological constant is treated as thermodynamic pressure. Our results underscore the universality of thermodynamic laws across classical and quantum regimes and highlight ongoing challenges in reconciling gravity with quantum theory. This review not only synthesizes current understanding of black hole thermodynamics and microscopic structure but also outlines promising directions for future research in quantum gravity.