English

Graded components of local cohomology modules of $\mathfrak{C}$-monomial ideals in characteristic zero

Commutative Algebra 2023-07-10 v1

Abstract

Let AA be a commutative Noetherian ring of characteristic zero and R=A[X1,,Xd]R=A[X_1, \ldots, X_d] be a polynomial ring over AA with the standard Nd\mathbb{N}^d-grading. Let IRI\subseteq R be an ideal which can be generated by elements of the form aUaU where aAa \in A (possibly nonunit) and UU is a monomial in XiX_i's. We call such an ideal as a `C\mathfrak{C}-monomial ideal'. Local cohomology modules supported on monomial ideals gain a great deal of interest due to their applications in the context of toric varieties. It was observed that for uZd\underline{u} \in \mathbb{Z}^d, their uth\underline{u}^{th} components depend only on which coordinates of u\underline{u} are negative. In this article, we show that this statement holds true in our general setting, even for certain invariants of the components. We mainly focus on the Bass numbers, injective dimensions, dimensions, associated primes, Bernstein-type dimensions, and multiplicities of the components. Under the extra assumption that AA is regular, we describe the finiteness of Bass numbers of each component and bound its injective dimension by the dimension of its support. Finally, we present a structure theorem for the components when AA is the ring of formal power series in one variable over a characteristic zero field.

Keywords

Cite

@article{arxiv.2307.03574,
  title  = {Graded components of local cohomology modules of $\mathfrak{C}$-monomial ideals in characteristic zero},
  author = {Tony J. Puthenpurakal and Sudeshna Roy},
  journal= {arXiv preprint arXiv:2307.03574},
  year   = {2023}
}