Higher-curvature corrections and the endpoint of black hole evaporation in gravitational effective field theory

The endpoint of black hole evaporation remains uncertain once the semiclassical description approaches the Planck scale. In this work we study late-stage evaporation within four-dimensional gravitational effective field theory. We consider the leading local correction to the Schwarzschild solution arising from a cubic curvature operator, and use the corrected geometry to analyze the resulting evaporation dynamics and associated thermodynamic properties. We show that the cubic correction induces a parametric slow-down of the evaporation rate at small masses, which within the truncated theory can appear as a freeze-out at a finite mass scale. We demonstrate that this behavior is not an independent physical prediction, but instead occurs precisely when the dimensionless expansion parameter of the effective theory becomes of order unity. The corresponding mass scale coincides parametrically with the onset of Planckian curvature at the horizon, establishing that the evaporation dynamics provide a direct diagnostic of the breakdown of the effective field theory. A scaling analysis of higher-order curvature operators shows that once the cubic term becomes comparable to the Einstein-Hilbert contribution, generic higher-order terms are no longer parametrically suppressed. The apparent remnant-like behavior therefore arises at the boundary of validity of the effective description rather than within a controlled perturbative regime. These results demonstrate that late-stage evaporation encodes the limits of gravitational effective field theory, providing a dynamical criterion for its breakdown.