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Mathematische Zeitschrift

, Volume 288, Issue 3–4, pp 783–802 | Cite as

Stability of test ideals of divisors with small multiplicity

  • Kenta Sato
Article
  • 78 Downloads

Abstract

Let \((X, \varDelta )\) be a log pair in characteristic \(p>0\) and P be a (not necessarily closed) point of X. We show that there exists a constant \(\delta >0\) such that the test ideal \(\tau (X, \varDelta )\), a characteristic p analogue of a multiplier ideal, does not change at P under the perturbation of \(\varDelta \) by any \(\mathbb {R}\)-divisor with multiplicity less than \(\delta \). As an application, we prove that if D is an \(\mathbb {R}\)-Cartier \(\mathbb {R}\)-divisor on a strongly F-regular projective variety, then the non-nef locus of D coincides with the restricted base locus of D. This is a generalization of a result of Mustaţǎ to the singular case and can be viewed as a characteristic p analogue of a result of Cacciola–Di Biagio.

Keywords

Test ideals Strongly F-regular singularities Restricted base loci Non-nef loci 

Mathematics Subject Classification

13A35 14A10 14B05 

Notes

Acknowledgements

The author wishes to express his gratitude to his supervisor Professor Shunsuke Takagi for his encouragement, valuable advice and suggestions. He is grateful to Doctor Sho Ejiri for his encouragement. He is also grateful to an anonymous referee for many useful suggestions and for pointing out many typos. This work was supported by the Program for Leading Graduate Schools, MEXT, Japan.

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Copyright information

© Springer-Verlag GmbH Deutschland 2017

Authors and Affiliations

  1. 1.Graduate School of Mathematical ScienceThe University of TokyoTokyoJapan

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