Verified spherical evolution in quadratic Palatini gravity: a controlled apparent-horizon comparison

Abstract

This preprint presents and verifies a spherical numerical formulation for a complex scalar field in quadratic Palatini gravity and uses it to compare apparent-horizon onset with general relativity. For constraint-solved data at dimensionless coupling ξ = 0.1, the physical onset radius is 19.56% smaller than in a charge/maximum-compactness-matched GR control and 23.92% smaller than in a same-seed GR control at the finest common grid. A further Palatini refinement and separate Richardson estimates support the resolved comparison. A documented numerical and physical-frame verification hierarchy bounds the principal implementation and representation failures. An action-level equilibrium check reconciles a public coefficient inconsistency and reproduces the published mass tabulation. A fixed-grid four-coupling scan is non-ordered, so the one-coupling result is not generalized to a monotonic coupling law. This record contains the streamlined manuscript, its companion reproducibility supplement, and a self-contained source archive including derivations, test definitions, machine-readable outcome records, and the associated verification pipeline.