The additive completion of the biset category

Jesús Ibarra, Alberto G. Raggi-Cárdenas, Nadia Romero

Let $R$ be a commutative unital ring. We construct a category ${\mathcal{C}}_R$ of fractions $X/G$, where $G$ is a finite group and $X$ is a finite $G$-set, and with morphisms given…