English

The jumping coefficients of non-Q-Gorenstein multiplier ideals

Algebraic Geometry 2020-11-10 v2

Abstract

Let aOX\mathfrak a \subset \mathscr O_X be a coherent ideal sheaf on a normal complex variety XX, and let c0c \ge 0 be a real number. De Fernex and Hacon associated a multiplier ideal sheaf to the pair (X,ac)(X, \mathfrak a^c) which coincides with the usual notion whenever the canonical divisor KXK_X is Q\mathbb Q-Cartier. We investigate the properties of the jumping numbers associated to these multiplier ideals. We show that the set of jumping numbers of a pair is unbounded, countable and satisfies a certain periodicity property. We then prove that the jumping numbers form a discrete set of real numbers if the locus where KXK_X fails to be Q\mathbb Q-Cartier is zero-dimensional. It follows that discreteness holds whenever XX is a threefold with rational singularities. Furthermore, we show that the jumping numbers are rational and discrete if one removes from XX a closed subset WXW \subset X of codimension at least three, which does not depend on a\mathfrak a. We also obtain that outside of WW, the multiplier ideal reduces to the test ideal modulo sufficiently large primes p0p \gg 0.

Keywords

Cite

@article{arxiv.1410.5091,
  title  = {The jumping coefficients of non-Q-Gorenstein multiplier ideals},
  author = {Patrick Graf},
  journal= {arXiv preprint arXiv:1410.5091},
  year   = {2020}
}