Topological Interpretations in Anisotropic Kerr-Newman-AdS Black Hole Thermodynamics
The interplay between black hole thermodynamics and topology provides a strong, coordinate-independent framework for discovering the underlying structure of black hole phase transitions as well as their universal features. We explore the thermodynamic topology of the anisotropic Kerr-Newman-AdS black hole using Duan's $ϕ$-mapping theory and a complex residue approach. By creating the generalized off-shell free energy, we propose a thermodynamic vector field in the parameter space with zero points corresponding to equilibrium black hole states. The winding numbers associated with these defects are utilized to calculate the black hole's global topological number. We begin with an analysis of the entire anisotropic Kerr-Newman-AdS black hole, followed by two limiting examples. Setting the anisotropic parameter $K = 0$ produces the Kerr-Newman-AdS black hole, while eliminating the AdS contribution produces the Kerr-Newman black hole. The anisotropic Kerr-Newman-AdS and Kerr-Newman-AdS black holes have a single thermodynamic defect with winding number $+1$, which results in $W = +1$. In contrast, the Kerr-Newman black hole has two defects with winding numbers $+1$ and $-1$, which result in a vanishing global topological number, $W = 0$. These findings show that the AdS contribution alters the global topological classification, but the anisotropic matter studied here preserves the topological class of the Kerr-Newman-AdS black hole. As an analogous limiting instance, we further study a Kiselev-type black hole, analyzing the circumstances in which its metric reduces to a charged black-hole geometry and how the thermodynamic topology reflects this reduction. Finally, we use the complex residue approach on the anisotropic Kerr-Newman-AdS black hole.