Next-Generation Improvements in Giant Exoplanet Evolutionary and Structural Models

Abstract: We present a comprehensive comparison between legacy and modern evolutionary models for giant exoplanets, using our planetary evolution code, APPLE, to emulate and extend previous studies. Our analysis isolates and quantifies the impact of recent physical advances motivated by detailed modeling of Jupiter and Saturn, including updated hydrogen-helium and heavy-element equations of state, helium rain, "fuzzy" cores, and non-adiabatic, inhomogeneous envelopes, alongside improved atmospheric boundary conditions that incorporate ammonia cloud physics. We first examine the influence of each new physical ingredient individually, then construct combined baseline models for masses between 0.3 to 4 Jupiter masses to assess their collective effect on planetary structure and observable properties. We find that the adoption of modern equations of state and realistic heavy-element distributions leads to systematic, but sometimes subtle, differences (~5 to 10%) in radius evolution, while helium rain and the treatment of convection can significantly alter thermal histories and atmospheric compositions (by ~5 to 20%). These updated physical processes must be incorporated into the next-generation exoplanet evolutionary models to achieve physically consistent interpretations of planetary observations.