Test ideals can be computed by boundaries

Rahul Ajit, with Appendix joint with Daniel Apsley

Let $R$ be a normal $F$-finite ring of characteristic $p>0$. We show that one effective $\mathbb{Q}$-divisor $\Delta$, with $K_R+\Delta$ $\mathbb{Q}$-Cartier of index prime to $p$, computes…