Test Modules of Extended Rees Algebras

Fuente: arXiv
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Autores principales: Ajit, Rahul, Simper, Hunter
Formato: Preprint
Publicado: 2025
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author Ajit, Rahul
Simper, Hunter
author_facet Ajit, Rahul
Simper, Hunter
contents Given a reduced, local ring $R$ and an ideal $\mathfrak{a}$ of positive height, we give a decomposition of the test module, $τ(ω_T, t^{-λ})$, of the extended Rees algebra, $T =R[\mathfrak{a} t, t^{-1}]$. In particular, the degree zero component of this test module is $τ(R, \mathfrak{a}^λ)$, thereby reducing the computation of test modules for non-principal ideals to the much easier case of principal ideals. Additionally, we apply our decomposition to generalize results on the $F$-rationality of Rees and extended Rees algebras [HWY02a, Conjecture 4.1],[KK21] as well as give simplified proofs of discreteness and rationality of F-jumping numbers, among other applications.
format Preprint
id arxiv_https___arxiv_org_abs_2509_01693
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Test Modules of Extended Rees Algebras
Ajit, Rahul
Simper, Hunter
Commutative Algebra
Algebraic Geometry
14F18, 14B05, 13A35
Given a reduced, local ring $R$ and an ideal $\mathfrak{a}$ of positive height, we give a decomposition of the test module, $τ(ω_T, t^{-λ})$, of the extended Rees algebra, $T =R[\mathfrak{a} t, t^{-1}]$. In particular, the degree zero component of this test module is $τ(R, \mathfrak{a}^λ)$, thereby reducing the computation of test modules for non-principal ideals to the much easier case of principal ideals. Additionally, we apply our decomposition to generalize results on the $F$-rationality of Rees and extended Rees algebras [HWY02a, Conjecture 4.1],[KK21] as well as give simplified proofs of discreteness and rationality of F-jumping numbers, among other applications.
title Test Modules of Extended Rees Algebras
topic Commutative Algebra
Algebraic Geometry
14F18, 14B05, 13A35
url https://arxiv.org/abs/2509.01693