scholarly journals An upper bound for the first Hilbert coefficient of Gorenstein algebras and modules

2021 ◽  
pp. 195-206
Author(s):  
Sabine El Khoury ◽  
Manoj Kummini ◽  
Hema Srinivasan
Keyword(s):  
Polynomial Ring ◽  
Upper Bound ◽  
Free Resolution ◽  
Degree Zero ◽  
Finitely Generated ◽  
Minimal Free Resolution ◽  
Content Type ◽  
Gorenstein Algebras ◽  
Gorenstein Algebra ◽  
Hilbert Coefficient

Let R R be a polynomial ring over a field and M = ⨁ n M n M= \bigoplus _n M_n be a finitely generated graded R R -module, minimally generated by homogeneous elements of degree zero with a graded R R -minimal free resolution F \mathbf {F} . A Cohen-Macaulay module M M is Gorenstein when the graded resolution is symmetric. We give an upper bound for the first Hilbert coefficient, e 1 e_1 in terms of the shifts in the graded resolution of M M . When M = R / I M = R/I , a Gorenstein algebra, this bound agrees with the bound obtained in [ES09] in Gorenstein algebras with quasi-pure resolution. We conjecture a similar bound for the higher coefficients.

On the Hilbert Coefficients and Betti Numbers of the Stanley-Reisner Ring of a Matroid Complex

2013 ◽  
Vol 20 (01) ◽  
pp. 47-58
Author(s):  
N. Shirmohammadi
Keyword(s):  
Polynomial Ring ◽  
Upper Bound ◽  
Betti Number ◽  
Betti Numbers ◽  
Free Resolution ◽  
Finitely Generated ◽  
Hilbert Coefficients ◽  
Hilbert Coefficient

Let S=K[x1,…,xn] be a polynomial ring. Herzog and Zheng conjectured that the i-th Hilbert coefficient of a finitely generated graded Cohen-Macaulay S-module N generated in degree 0 is bounded by the functions of the minimal and maximal shifts in the minimal graded free resolution of N over S and the 0-th Betti number of N. Also, Römer asked whether under the Cohen-Macaulay assumption the i-th Betti number of S/I, where I ⊂ S is a graded ideal, can be bounded by the functions of the minimal and maximal shifts of S/I. In this paper, we provide elementary proofs to establish Herzog and Zheng's conjecture and the upper bound part of Römer's question for the Stanley-Reisner ring of a matroid complex.

𝐿-dimension for modules over a local ring

2021 ◽  
pp. 83-91
Author(s):  
Courtney Gibbons ◽  
David Jorgensen ◽  
Janet Striuli
Keyword(s):  
Local Ring ◽  
Complete Intersection ◽  
Residue Field ◽  
Free Resolution ◽  
Homological Dimension ◽  
Finitely Generated ◽  
Content Type ◽  
Commutative Local Ring ◽  
Finitely Generated Modules

We introduce a new homological dimension for finitely generated modules over a commutative local ring R R , which is based on a complex derived from a free resolution L L of the residue field of R R , and called L L -dimension. We prove several properties of L L -dimension, give some applications, and compare L L -dimension to complete intersection dimension.

scholarly journals ON THE ASYMPTOTIC BEHAVIOR OF THE LINEARITY DEFECT

2017 ◽  
Vol 230 ◽  
pp. 35-47 ◽  
Author(s):  
HOP D. NGUYEN ◽  
THANH VU
Keyword(s):  
Asymptotic Behavior ◽  
Local Ring ◽  
General Result ◽  
Free Resolution ◽  
Graded Algebra ◽  
Regular Local Ring ◽  
Finitely Generated ◽  
Minimal Free Resolution ◽  
Noetherian Local Ring ◽  
Graded Module

This work concerns the linearity defect of a module $M$ over a Noetherian local ring $R$, introduced by Herzog and Iyengar in 2005, and denoted $\text{ld}_{R}M$. Roughly speaking, $\text{ld}_{R}M$ is the homological degree beyond which the minimal free resolution of $M$ is linear. It is proved that for any ideal $I$ in a regular local ring $R$ and for any finitely generated $R$-module $M$, each of the sequences $(\text{ld}_{R}(I^{n}M))_{n}$ and $(\text{ld}_{R}(M/I^{n}M))_{n}$ is eventually constant. The first statement follows from a more general result about the eventual constancy of the sequence $(\text{ld}_{R}C_{n})_{n}$ where $C$ is a finitely generated graded module over a standard graded algebra over $R$.

scholarly journals On the Stanley Depth of Powers of Monomial Ideals

Mathematics ◽  
2019 ◽  
Vol 7 (7) ◽  
pp. 607 ◽  
Author(s):  
S. A. Seyed Fakhari
Keyword(s):  
Polynomial Ring ◽  
Upper Bound ◽  
Integral Closure ◽  
Monomial Ideals ◽  
The Other ◽  
Finitely Generated ◽  
Stanley Depth ◽  
Survey Article ◽  
Symbolic Powers ◽  
Other Hand

In 1982, Stanley predicted a combinatorial upper bound for the depth of any finitely generated multigraded module over a polynomial ring. The predicted invariant is now called the Stanley depth. Duval et al. found a counterexample for Stanley’s conjecture, and their counterexample is a quotient of squarefree monomial ideals. On the other hand, there is evidence showing that Stanley’s inequality can be true for high powers of monomial ideals. In this survey article, we collect the recent results in this direction. More precisely, we investigate the Stanley depth of powers, integral closure of powers, and symbolic powers of monomial ideals.

The second Hilbert coefficient of modules with almost maximal depth

2019 ◽  
Vol 18 (12) ◽  
pp. 1950240
Author(s):  
Van Duc Trung
Keyword(s):  
Lower Bound ◽  
Local Ring ◽  
Upper Bound ◽  
Primary Ideal ◽  
Finitely Generated ◽  
Dimension Formula ◽  
Maximal Depth ◽  
Graded Module ◽  
Hilbert Coefficient

Let [Formula: see text] be a good [Formula: see text]-filtration of a finitely generated [Formula: see text]-module [Formula: see text] of dimension [Formula: see text], where [Formula: see text] is a local ring and [Formula: see text] is an [Formula: see text]-primary ideal of [Formula: see text]. In the case of depth [Formula: see text], we give an upper bound for the second Hilbert coefficient [Formula: see text] generalizing the results by Huckaba–Marley, and Rossi–Valla proved that [Formula: see text] is Cohen–Macaulay. We also give a condition for the equality, which relates to the depth of the associated graded module [Formula: see text]. A lower bound on [Formula: see text] is proved generalizing a result by Rees and Narita.

scholarly journals Homology of Powers of Ideals: Artin-Rees Numbers of Syzygies and the Golod Property

2016 ◽  
Vol 23 (04) ◽  
pp. 689-700 ◽  
Author(s):  
Jürgen Herzog ◽  
Volkmar Welker ◽  
Siamak Yassemi
Keyword(s):  
Polynomial Ring ◽  
Residue Class ◽  
Betti Numbers ◽  
Free Resolution ◽  
Minimal Free Resolution ◽  
Powers Of Ideals ◽  
Residue Class Field ◽  
Syzygy Modules ◽  
Free Modules ◽  
Specific Degree

Let R0 be a Noetherian local ring and R a standard graded R0-algebra with maximal ideal 𝔪 and residue class field 𝕂 = R/𝔪. For a graded ideal I in R we show that for k ≫ 0: (1) the Artin-Rees number of the syzygy modules of Ik as submodules of the free modules from a free resolution is constant, and thereby the Artin-Rees number can be presented as a proper replacement of regularity in the local situation; and (2) R is a polynomial ring over the regular R0, the ring R/Ik is Golod, its Poincaré-Betti series is rational and the Betti numbers of the free resolution of 𝕂 over R/Ik are polynomials in k of a specific degree. The first result is an extension of the work by Swanson on the regularity of Ik for k ≫ 0 from the graded situation to the local situation. The polynomiality consequence of the second result is an analog of the work by Kodiyalam on the behaviour of Betti numbers of the minimal free resolution of R/Ik over R.

scholarly journals Curves with Two Pencils and Associated Maps to Projective Spaces

2006 ◽  
Vol 13 (3) ◽  
pp. 411-417
Author(s):  
Edoardo Ballico
Keyword(s):  
Linear System ◽  
Projective Spaces ◽  
Free Resolution ◽  
Homogeneous Ideal ◽  
Projective Curve ◽  
Minimal Free Resolution ◽  
Complete Linear System

Abstract Let 𝑋 be a smooth and connected projective curve. Assume the existence of spanned 𝐿 ∈ Pic𝑎(𝑋), 𝑅 ∈ Pic𝑏(𝑋) such that ℎ0(𝑋, 𝐿) = ℎ0(𝑋, 𝑅) = 2 and the induced map ϕ 𝐿,𝑅 : 𝑋 → 𝐏1 × 𝐏1 is birational onto its image. Here we study the following question. What can be said about the morphisms β : 𝑋 → 𝐏𝑅 induced by a complete linear system |𝐿⊗𝑢⊗𝑅⊗𝑣| for some positive 𝑢, 𝑣? We study the homogeneous ideal and the minimal free resolution of the curve β(𝑋).

Branched Coverings and Minimal Free Resolution for Infinite-Dimensional Complex Spaces

2003 ◽  
Vol 10 (1) ◽  
pp. 37-43
Author(s):  
E. Ballico
Keyword(s):  
Projective Space ◽  
Projective Spaces ◽  
Free Resolution ◽  
Complete Intersections ◽  
Vanishing Theorem ◽  
Sheaf Cohomology ◽  
Minimal Free Resolution ◽  
Branched Coverings ◽  
Infinite Dimensional ◽  
Complex Spaces

Abstract We consider the vanishing problem for higher cohomology groups on certain infinite-dimensional complex spaces: good branched coverings of suitable projective spaces and subvarieties with a finite free resolution in a projective space P(V ) (e.g. complete intersections or cones over finitedimensional projective spaces). In the former case we obtain the vanishing result for H 1. In the latter case the corresponding results are only conditional for sheaf cohomology because we do not have the corresponding vanishing theorem for P(V ).

scholarly journals A note on the subadditivity of Syzygies

2016 ◽  
Vol 16 (09) ◽  
pp. 1750177 ◽  
Author(s):  
Sabine El Khoury ◽  
Hema Srinivasan
Keyword(s):  
Free Resolution ◽  
Graded Algebra ◽  
Gorenstein Algebras

Let [Formula: see text] be a graded algebra with [Formula: see text] and [Formula: see text] being the minimal and maximal shifts in the minimal graded free resolution of [Formula: see text] at degree [Formula: see text]. We prove that [Formula: see text] for all [Formula: see text]. As a consequence, we show that for Gorenstein algebras of codimension [Formula: see text], the subadditivity of maximal shifts [Formula: see text] in the minimal graded free resolution holds for [Formula: see text], i.e. we show that [Formula: see text] for [Formula: see text].

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