On the Geometry of Solutions of the Fully Nonlinear Inhomogeneous One-Phase Stefan Problem

In this paper, we characterize the geometry of solutions to one-phase inhomogeneous fully nonlinear Stefan problem with flat free boundaries under a new nondegeneracy assumption. This continues the study of regularity of flat free boundaries for the linear inhomogeneous Stefan problem started in [9], as well as justifies the definition of flatness assumed in [15].