Thermodynamics of Flat 4D Einstein-Gauss-Bonnet Black Hole with Rényi Entropy: An RPST-like formalism

Abstract: We investigate the thermodynamics of asymptotically flat black holes in four-dimensional Einstein-Gauss-Bonnet (4D-EGB) gravity using R\'enyi entropy as a non-extensive generalization of the Bekenstein-Hawking entropy. The resulting thermodynamic structure, formulated within a restricted phase space-like (RPST-like) framework, reveals a striking resemblance to the thermodynamics of AdS black holes in the standard RPST formalism. In particular, we identify a thermodynamic duality between the R\'enyi deformation parameter $\beta$ and a conjugate response potential $\zeta$, analogous to the central charge and chemical potential in holographic theories. An extensive thermodynamic analysis in both fixed charge-$(\tilde{Q})$ and fixed potential-$(\tilde{\Phi})$ ensembles reveal Van der Waals-like first-order phase transitions which is an unexpected feature for asymptotically flat black holes. Furthermore, through the formalism of geometrothermodynamics (GTD), we show that the thermodynamic geometry of the R\'enyi-modified flat black hole mimics that of the AdS black hole under RPST, reinforcing the structural similarity between these seemingly different systems. Our findings point to a deeper correspondence between non-extensive entropy and holographic thermodynamics, suggesting that R\'enyi entropy may serve as a natural bridge between flat-space black hole thermodynamics and AdS holography.