F-signature exists

K Tucker - Inventiones mathematicae, 2012 - Springer
Suppose R is ad-dimensional reduced F-finite Noetherian local ring with prime characteristic
p> 0 and perfect residue field. Let R^1/p^e be the ring of pe-th roots of elements of R for e∈ …

Quantifying singularities with differential operators

H Brenner, J Jeffries, L Núñez-Betancourt - Advances in Mathematics, 2019 - Elsevier
The F-signature of a local ring of prime characteristic is a numerical invariant that detects
many interesting properties. For example, this invariant detects (non) singularity and strong …

[PDF][PDF] A survey of test ideals

K Schwede, K Tucker - Progress in commutative algebra, 2012 - library.oapen.org
Test ideals were first introduced by Mel Hochster and Craig Huneke in their celebrated
theory of tight closure, and since their invention have been closely tied to the theory of …

F-signature and Hilbert–Kunz multiplicity: a combined approach and comparison

T Polstra, K Tucker - Algebra & Number Theory, 2018 - msp.org
We present a unified approach to the study of F-signature, Hilbert–Kunz multiplicity, and
related limits governed by Frobenius and Cartier linear actions in positive characteristic …

Perfectoid signature, perfectoid Hilbert-Kunz multiplicity, and an application to local fundamental groups

H Cai, S Lee, L Ma, K Schwede, K Tucker - arXiv preprint arXiv …, 2022 - arxiv.org
We define a (perfectoid) mixed characteristic version of $ F $-signature and Hilbert-Kunz
multiplicity by utilizing the perfectoidization functor of Bhatt-Scholze and Faltings' normalized …

The structure of F-pure rings

IM Aberbach, F Enescu - Mathematische Zeitschrift, 2005 - Springer
For a reduced F-finite ring R of characteristic p> 0 and q= pe one can write where M q has
no free direct summands over R. We investigate the structure of F-finite, F-pure rings R by …

Fundamental groups of -regular singularities via -signature

J Carvajal-Rojas, K Schwede, K Tucker - arXiv preprint arXiv:1606.04088, 2016 - arxiv.org
We prove that the local etale fundamental group of a strongly $ F $-regular singularity is
finite (and likewise for the\'etale fundamental group of the complement of a codimension …

Observations on the F-signature of local rings of characteristic p

Y Yao - Journal of Algebra, 2006 - Elsevier
Let (R, m, k) be a d-dimensional Noetherian reduced local ring of prime characteristic p such
that [Formula: see text] are finite over R for all e∈ N (ie R is F-finite). Consider the sequence …

[PDF][PDF] F-singularities: a commutative algebra approach

L Ma, T Polstra - Preprint avalable at https://www. math. purdue …, 2021 - math.purdue.edu
The local theory of prime characteristic singularities is a beautiful and historied subject.
Singularities which are defined in terms of the behavior of the Frobenius endomorphism …

Minimal relative Hilbert-Kunz multiplicity

K Watanabe, K Yoshida - Illinois Journal of Mathematics, 2004 - projecteuclid.org
In this paper we ask the following question: What is the minimal value of the difference $\ehk
(I)-\ehk (I') $ for ideals $ I'\supseteq I $ with $ l_A (I'/I)= 1$? In order to answer to this …