Abstract DGP2026-111

Gas giants accumulate most of their mass during the runaway gas accretion stage, during which the infalling gas forms strong shocks exterior to the planetary surface. The post-shock states profoundly influence the subsequent evolution and the initial thermodynamic structure of young gas giants. Using Guangqi code with a realistic equation of state (EoS) including hydrogen dissociation, we performed thousands of simulations to systematically explore a wide parameter space: planetary mass and radius, accretion rate, and the internal luminosity of forming gas giants, with explicit focus on post-shock states. Furthermore, we develop a physics-informed neural network (PINN) trained on the simulation results. This PINN provides instantaneous post-shock states predictions, offering realistic boundary conditions for interior evolution codes like MESA. Our findings suggest that a “warm-start” evolution regime associated with partial H₂ dissociation is the most plausible formation pathway for gas giant, with potentially applicable implications for the origin of Jupiter.