Rival-Injective Allocations: Support-List Structure and Maximum-Anchor EFX$_0$ Certificates
We study complete allocations under nonnegative additive valuations through the positive supports of goods, focusing on the all-good form of envy-freeness up to any good (EFX$_0$). We define rival-injective (RI) endpoint ownership: every good with nonempty positive support is assigned to an agent who values it positive...