F-singularities via alterations

TL;DR

This paper provides a unified description of multiplier and test ideals for pairs on normal F-finite varieties using regular alterations, linking singularity types and extending vanishing theorems in positive characteristic.

Contribution

It introduces a uniform ideal description via alterations that characterizes rational and F-rational singularities and extends key vanishing theorems without lifting assumptions.

Findings

Unified description of multiplier and test ideals via alterations.

Characterization of rational and F-rational singularities through trace map surjectivity.

Extended vanishing theorems in positive characteristic without W2 lifting.

Abstract

For a normal F-finite variety $X$ and a boundary divisor $\Delta$ we give a uniform description of an ideal which in characteristic zero yields the multiplier ideal, and in positive characteristic the test ideal of the pair $(X,\Delta)$. Our description is in terms of regular alterations over $X$, and one consequence of it is a common characterization of rational singularities (in characteristic zero) and F-rational singularities (in characteristic $p$) by the surjectivity of the trace map $\pi_* \omega_Y \to \omega_X$ for every such alteration $\pi \: Y \to X$. Furthermore, building on work of B. Bhatt, we establish up-to-finite-map versions of Grauert-Riemenscheneider and Nadel/Kawamata-Viehweg vanishing theorems in the characteristic $p$ setting without assuming $W2$ lifting, and show that these are strong enough in some applications to extend sections.