Thermodynamic topology of AdS black holes with $F^{αβ}F^{γλ}R_{αγ}R_{βλ}$ coupling in the grand canonical ensemble
Year: 2026
Type: preprint
Abstract: We investigate the thermodynamic and topological phase structure of charged AdS black holes with a nonminimal gauge--curvature coupling in the grand canonical ensemble. In the minimal-coupling limit $ε=0$, the system exhibits only Hawking--Page-like behavior and does not possess van der Waals criticality. Working perturbatively in the nonminimal coupling, we find that the $ε\neq0$ interaction generates a rich phase structure as the electric potential is varied, including several distinct regimes of critical behavior, a double-critical region, and a regime where conventional criticality disappears. We complement the conventional thermodynamic analysis with a topological description based on the winding number of the thermodynamic vector field. The resulting $r_h$--$τ$ diagrams reveal that the ordering and morphology of the black-hole branches depend sensitively on both the pressure and the off-shell inverse temperature, with monotonic, disconnected, S-shaped, and cusp-like structures appearing in different parameter ranges. Remarkably, these substantial rearrangements of the solution branches can occur without changing the global winding number. In particular, the system remains in the $W=+1$ topological class beyond the range of conventional criticality, before eventually entering a $W=0$ sector. Our results demonstrate that thermodynamic topology provides complementary global information that is not captured by conventional local criticality criteria alone.
Source: arXiv (Cornell University)
Authors: Rahmani, Faramarz, Sadeghi, Mehdi
Institution: Ayatollah Boroujerdi University
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7212963910