Kaniadakis Holographic Dark Energy: UV–IR Duality, Horizon Thermodynamics, and Cosmological Constraints

ABSTRACT

We investigate the cosmological and thermodynamic implications of holographic dark energy derived from the Kaniadakis deformation of the Bekenstein–Hawking entropy. In a spatially flat FLRW universe, the generalized entropy generates an effective dark‐energy density with an infrared correction proportional to , naturally producing an ultraviolet–infrared structure in the cosmological dynamics. Using the Hayward–Kodama formulation of apparent‐horizon thermodynamics, we derive a geometric equation of state and identify Van der Waals‐type criticality, characterized by an inverted first‐order phase transition and an inverted swallowtail Gibbs potential. We interpret this behavior as the thermodynamic signature of a geometric phase transition of the apparent horizon rather than standard fluid coexistence. We also consider an extended model with a contribution inspired by the Granda–Oliveros cutoff and show that this unconventional critical behavior persists. At the perturbative level, the same ultraviolet–infrared competition controls the effective sound speed and dark‐energy response through a dimensionless coupling , which acts as a geometric order parameter. In the minimal model, may cross zero during matter domination, marking a transition between infrared‐ and ultraviolet‐dominated regimes, whereas the extended scenario remains ultraviolet dominated. Finally, we confront both models with cosmic chronometers, PantheonPlus Type Ia supernovae, DESI DR2 baryon acoustic oscillations, and redshift‐space distortion data. Bayesian comparison with , CPL, and standard holographic dark energy strongly disfavors the minimal model. The extended model yields the best maximum‐likelihood fit among those considered, but remains disfavored relative to after accounting for its larger parameter volume.