Topological Complex Analysis of Kerr--Newman Black Hole Microstructure in f(R) Gravity

Abstract: We investigate the microstructure of Kerr Newman black holes in modified gravity of the f(R) type using a topological complex analytic framework inspired by holography. In this approach, black hole microstates are identified with singularities of an analytically continued partition function, and the entropy is obtained from residues weighted by winding numbers. We show that the microstructure is characterized by a discrete topological index, which encodes both horizon structure and thermodynamic stability. Non extremal Kerr Newman black holes with both inner and outer horizons correspond to a vanishing topological index, while single horizon configurations correspond to a positive unit topological index. An explicit Starobinsky type modified gravity model demonstrates that this classification is robust under changes to the gravitational sector. We further discuss the limitations of the analytic continuation procedure and suggest that this topological classification may indicate a form of phase protection in black hole thermodynamics.