English

A sufficient condition for finiteness of Frobenius test exponents

Commutative Algebra 2021-02-03 v4

Abstract

The Frobenius test exponent Fte(R)\operatorname{Fte}(R) of a local ring (R,m)(R,\mathfrak{m}) of prime characteristic p>0p > 0 is the smallest e0Ne_0 \in \mathbb{N} such that for every ideal q\mathfrak{q} generated by a (full) system of parameters, the Frobenius closure qF\mathfrak{q}^F has (qF)[pe0]=q[pe0](\mathfrak{q}^F)^{[p^{e_0}]} = \mathfrak{q}^{[p^{e_0}]}. We establish a suffcient condition for Fte(R)<\operatorname{Fte}(R)<\infty and use it to show that if RR is such that the Frobenius closure of the zero submodule in the lower local cohomology modules has finite colength, i.e. Hmj(R)/0Hmj(R)FH^j_{\mathfrak{m}}(R) / 0^F_{H^j_{\mathfrak{m}}(R)} is finite length for 0j<dim(R)0 \le j < \dim(R), then Fte(R)<\operatorname{Fte}(R)<\infty.

Keywords

Cite

@article{arxiv.1809.10063,
  title  = {A sufficient condition for finiteness of Frobenius test exponents},
  author = {Kyle Maddox},
  journal= {arXiv preprint arXiv:1809.10063},
  year   = {2021}
}

Comments

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