Regularity, singularities and $h$-vector of graded algebras
Fuente:
arXiv
Saved in:
| Main Authors: | , , |
|---|---|
| Format: | Preprint |
| Published: |
2019
|
| Subjects: | |
| Online Access: | |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1866914920978710528 |
|---|---|
| author | Dao, Hailong Ma, Linquan Varbaro, Matteo |
| author_facet | Dao, Hailong Ma, Linquan Varbaro, Matteo |
| contents | Let $R$ be a standard graded algebra over a field. We investigate how the singularities of $R$ affect its $h$-vector, which is the coefficients of the numerator of its Hilbert series. The most concrete consequences of our work asserts that if $R$ satisfies Serre's condition $(S_r)$ and have reasonable singularities (Du Bois on the punctured spectrum or $F$-pure), then $h_0,\dots, h_r\geq 0$. Furthermore the multiplicity of $R$ is at least $h_0+h_1+\dots+h_{r-1}$. We also prove that equality in many cases forces $R$ to be Cohen-Macaulay. The main technical tools are sharp bounds on regularity of certain Ext modules, which can be viewed as Kodaira-type vanishing statements for Du Bois and $F$-singularities. Many corollaries are deduced, for instance that nice singularities of small codimension must be Cohen-Macaulay. Our results build on and extend previous work by de Fernex-Ein, Eisenbud-Goto, Huneke-Smith, Murai-Terai and others. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_1901_01116 |
| institution | arXiv |
| publishDate | 2019 |
| record_format | arxiv |
| spellingShingle | Regularity, singularities and $h$-vector of graded algebras Dao, Hailong Ma, Linquan Varbaro, Matteo Commutative Algebra Algebraic Geometry Let $R$ be a standard graded algebra over a field. We investigate how the singularities of $R$ affect its $h$-vector, which is the coefficients of the numerator of its Hilbert series. The most concrete consequences of our work asserts that if $R$ satisfies Serre's condition $(S_r)$ and have reasonable singularities (Du Bois on the punctured spectrum or $F$-pure), then $h_0,\dots, h_r\geq 0$. Furthermore the multiplicity of $R$ is at least $h_0+h_1+\dots+h_{r-1}$. We also prove that equality in many cases forces $R$ to be Cohen-Macaulay. The main technical tools are sharp bounds on regularity of certain Ext modules, which can be viewed as Kodaira-type vanishing statements for Du Bois and $F$-singularities. Many corollaries are deduced, for instance that nice singularities of small codimension must be Cohen-Macaulay. Our results build on and extend previous work by de Fernex-Ein, Eisenbud-Goto, Huneke-Smith, Murai-Terai and others. |
| title | Regularity, singularities and $h$-vector of graded algebras |
| topic | Commutative Algebra Algebraic Geometry |
| url | https://arxiv.org/abs/1901.01116 |