scholarly journals The number of generators of the powers of an ideal

2019 ◽  
Vol 29 (05) ◽  
pp. 827-847 ◽  
Author(s):  
Jürgen Herzog ◽  
Maryam Mohammadi Saem ◽  
Naser Zamani
Keyword(s):  
Lower Bounds ◽  
Principal Ideal ◽  
Monomial Ideal ◽  
Ideal Formula ◽  
Number Of Generators ◽  
Regular Rings

We study the number of generators of ideals in regular rings and ask the question whether [Formula: see text] if [Formula: see text] is not a principal ideal, where [Formula: see text] denotes the number of generators of an ideal [Formula: see text]. We provide lower bounds for the number of generators for the powers of an ideal and also show that the CM-type of [Formula: see text] is [Formula: see text] if [Formula: see text] is a monomial ideal of height [Formula: see text] in [Formula: see text] and [Formula: see text].

scholarly journals Comparing powers of edge ideals

2019 ◽  
Vol 18 (10) ◽  
pp. 1950184 ◽  
Author(s):  
Mike Janssen ◽  
Thomas Kamp ◽  
Jason Vander Woude
Keyword(s):  
Symbolic Power ◽  
Edge Ideal ◽  
Homogeneous Ideal ◽  
Edge Ideals ◽  
Ideal Formula ◽  
Number Of Generators ◽  
Recent Interest ◽  
Odd Cycle ◽  
Ordinary Power

Given a nontrivial homogeneous ideal [Formula: see text], a problem of great recent interest has been the comparison of the [Formula: see text]th ordinary power of [Formula: see text] and the [Formula: see text]th symbolic power [Formula: see text]. This comparison has been undertaken directly via an exploration of which exponents [Formula: see text] and [Formula: see text] guarantee the subset containment [Formula: see text] and asymptotically via a computation of the resurgence [Formula: see text], a number for which any [Formula: see text] guarantees [Formula: see text]. Recently, a third quantity, the symbolic defect, was introduced; as [Formula: see text], the symbolic defect is the minimal number of generators required to add to [Formula: see text] in order to get [Formula: see text]. We consider these various means of comparison when [Formula: see text] is the edge ideal of certain graphs by describing an ideal [Formula: see text] for which [Formula: see text]. When [Formula: see text] is the edge ideal of an odd cycle, our description of the structure of [Formula: see text] yields solutions to both the direct and asymptotic containment questions, as well as a partial computation of the sequence of symbolic defects.

Noetherian domains in which every ideal is isomorphic to a trace ideal

2019 ◽  
Vol 19 (10) ◽  
pp. 2050200
Author(s):  
A. Mimouni
Keyword(s):  
Maximal Ideal ◽  
Noetherian Ring ◽  
Principal Ideal ◽  
Large Family ◽  
One Dimensional ◽  
Ideal Formula ◽  
Noetherian Domain ◽  
Trace Ideal

This paper seeks an answer to the following question: Let [Formula: see text] be a Noetherian ring with [Formula: see text]. When is every ideal isomorphic to a trace ideal? We prove that for a local Noetherian domain [Formula: see text] with [Formula: see text], every ideal is isomorphic to a trace ideal if and only if either [Formula: see text] is a DVR or [Formula: see text] is one-dimensional divisorial domain, [Formula: see text] is a principal ideal of [Formula: see text] and [Formula: see text] posses the property that every ideal of [Formula: see text] is isomorphic to a trace ideal of [Formula: see text]. Next, we globalize our result by showing that a Noetherian domain [Formula: see text] with [Formula: see text] has every ideal isomorphic to a trace ideal if and only if either [Formula: see text] is a PID or [Formula: see text] is one-dimensional divisorial domain, every invertible ideal of [Formula: see text] is principal and for every non-invertible maximal ideal [Formula: see text] of [Formula: see text], [Formula: see text] is a principal ideal of [Formula: see text] and every ideal of [Formula: see text] is isomorphic to a trace ideal of [Formula: see text]. We close the paper by examining some classes of non-Noetherian domains with this property to provide a large family of original examples.

scholarly journals Linear syzygies of Stanley-Reisner ideals

2001 ◽  
Vol 89 (1) ◽  
pp. 117 ◽  
Author(s):  
V Reiner ◽  
V Welker
Keyword(s):  
Simplicial Complex ◽  
Lower Bounds ◽  
Monomial Ideal ◽  
Independent Sets ◽  
Free Resolution ◽  
Monomial Ideals ◽  
Minimal Free Resolution ◽  
Linear Syzygies ◽  
Alexander Dual ◽  
Syzygy Modules

We give an elementary description of the maps in the linear strand of the minimal free resolution of a square-free monomial ideal, that is, the Stanley-Reisner ideal associated to a simplicial complex $\Delta$. The description is in terms of the homology of the canonical Alexander dual complex $\Delta^*$. As applications we are able to prove for monomial ideals and $j=1$ a conjecture of J. Herzog giving lower bounds on the number of $i$-syzygies in the linear strand of $j^{th}$-syzygy modules show that the maps in the linear strand can be written using only $\pm 1$ coefficients if $\Delta^*$ is a pseudomanifold exhibit an example where multigraded maps in the linear strand cannot be written using only $\pm 1$ coefficients compute the entire resolution explicitly when $\Delta^*$ is the complex of independent sets of a matroid

On the reduction numbers of monomial ideals

2019 ◽  
Vol 19 (10) ◽  
pp. 2050201
Author(s):  
Ibrahim Al-Ayyoub
Keyword(s):  
Polynomial Ring ◽  
Monomial Ideal ◽  
Upper Bounds ◽  
Integral Closure ◽  
Monomial Ideals ◽  
Explicit Method ◽  
Generating Set ◽  
Ideal Formula ◽  
Reduction Number ◽  
The Ideal

Let [Formula: see text] be a monomial ideal in a polynomial ring with two indeterminates over a field. Assume [Formula: see text] is contained in the integral closure of some ideal that is generated by two elements from the generating set of [Formula: see text]. We produce sharp upper bounds for each of the reduction number and the Ratliff–Rush reduction number of the ideal [Formula: see text]. Under certain hypotheses, we give the exact values of these reduction numbers, and we provide an explicit method for obtaining these sharp upper bounds.

QUASI-MORPHIC RINGS

2007 ◽  
Vol 06 (05) ◽  
pp. 789-799 ◽  
Author(s):  
V. CAMILLO ◽  
W. K. NICHOLSON
Keyword(s):  
Principal Ideal ◽  
Principal Ideal Ring ◽  
Bezout Ring ◽  
Ideal Ring ◽  
Left And Right ◽  
Regular Rings

A ring R is called left morphic if R/Ra ≅ l (a) for each a ∈ R, equivalently if there exists b ∈ R such that Ra = l (b) and l (a) = Rb. In this paper, we ask only that b and c exist such that Ra = l (b) and l (a) = Rc, and call R left quasi-morphic if this happens for every element a of R. This class of rings contains the regular rings and the left morphic rings, and it is shown that finite intersections of principal left ideals in such a ring are again principal. It is further proved that if R is quasi-morphic (left and right), then R is a Bézout ring and has the ACC on principal left ideals if and only if it is an artinian principal ideal ring.

A study of a family of monomial ideals

2021 ◽  
Author(s):  
J. William Hoffman ◽  
Haohao Wang
Keyword(s):  
Structural Properties ◽  
Monomial Ideal ◽  
Free Resolution ◽  
Monomial Ideals ◽  
Symmetric Algebra ◽  
Rees Algebra ◽  
Implicit Equation ◽  
Ideal Formula ◽  
Moving Planes

In this paper, we study a family of rational monomial parametrizations. We investigate a few structural properties related to the corresponding monomial ideal [Formula: see text] generated by the parametrization. We first find the implicit equation of the closure of the image of the parametrization. Then we provide a minimal graded free resolution of the monomial ideal [Formula: see text], and describe the minimal graded free resolution of the symmetric algebra of [Formula: see text]. Finally, we provide a method to compute the defining equations of the Rees algebra of [Formula: see text] using three moving planes that follow the parametrization.

scholarly journals Stanley depth of monomial ideals with small number of generators

2009 ◽  
Vol 7 (4) ◽  
Author(s):  
Mircea Cimpoeaş
Keyword(s):  
Monomial Ideal ◽  
Monomial Ideals ◽  
Stanley Depth ◽  
Number Of Generators ◽  
Stanley Conjecture

AbstractFor a monomial ideal I ⊂ S = K[x 1...,x n], we show that sdepth(S/I) ≥ n − g(I), where g(I) is the number of the minimal monomial generators of I. If I =νI′, where ν ∈ S is a monomial, then we see that sdepth(S/I) = sdepth(S/I′). We prove that if I is a monomial ideal I ⊂ S minimally generated by three monomials, then I and S/I satisfy the Stanley conjecture. Given a saturated monomial ideal I ⊂ K[x 1,x 2,x 3] we show that sdepth(I) = 2. As a consequence, sdepth(I) ≥ sdepth(K[x 1,x 2,x 3]//I) +1 for any monomial ideal in I ⊂ K[x 1,x 2,x 3].

Polynomials inducing the zero function on chain rings

2018 ◽  
Vol 17 (08) ◽  
pp. 1850160 ◽  
Author(s):  
Mark W. Rogers ◽  
Cameron Wickham
Keyword(s):  
Maximal Ideal ◽  
Principal Ideal ◽  
Valuation Ring ◽  
Residue Field ◽  
Discrete Valuation Ring ◽  
Minimal Set ◽  
Principal Ideal Ring ◽  
Ideal Formula ◽  
Zero Function ◽  
The Ideal

We provide a minimal set of generators for the ideal of polynomials in [Formula: see text] that map the maximal ideal [Formula: see text] into one of its powers [Formula: see text], where [Formula: see text] is a discrete valuation ring with a finite residue field. We use this to provide a minimal set of generators for the ideal of polynomials in [Formula: see text] that send [Formula: see text] to zero, where [Formula: see text] is a finite commutative local principal ideal ring.

The ideal structure of existentially closed algebras

1985 ◽  
Vol 50 (4) ◽  
pp. 1025-1043 ◽  
Author(s):  
Paul C. Eklof ◽  
Hans-Christian Mez
Keyword(s):  
Principal Ideal ◽  
Associative Algebras ◽  
Principal Ideals ◽  
Existential Formula ◽  
Existentially Closed ◽  
Necessary And Sufficient ◽  
Divisible Part ◽  
Prüfer Rings ◽  
Torsion Free ◽  
Regular Rings

Throughout this paper, ⊿ will denote a commutative ring with multiplicative identity, 1. The algebras we consider will be associative ⊿-algebras which are not necessarily commutative and do not necessarily contain a multiplicative identity. By standard methods, every ⊿-algebra can be embedded in an existentially closed (e.c.) Δ-algebra—and even in one which is existentially universal (e.u.). (See §0 for more details.)We shall be studying the ideals of e.c. ⊿-algebras. Since every ideal is a sum of principal ideals, a natural place to begin is with principal ideals. In §1 we show that for an algebraically closed (a.c.) ⊿-algebra A, and elements a, b in A, whether or not b belongs to the principal ideal (a)A generated by a, depends only on the underlying ⊿-module structure of A; more precisely, for b to belong to (a)A it is necessary and sufficient that b satisfies every positive existential formula θ(ν) in the language of ⊿-modules which is satisfied by a (cf. Corollary 1.8). For special classes of rings ⊿ this condition can be simplified (Proposition 1.10): e.g. for Prüfer rings it is enough to consider formulas of the form ∃x(λx = μν); and for regular rings it is enough to consider formulas μν = 0 (where λ, μ ∈ ⊿).In §2 we use the results of §1 to study e.c. and e.u. algebras over a principal ideal domain (p.i.d.) ⊿ (Note that for ⊿ = Z this includes the case of e.c. rings.) We obtain a necessary and sufficient condition for an a.c. ⊿-algebra to be e.c. (Theorem 2.4). We also show (Theorem 2.2) that in an a.c. ⊿-algebra A every element that is divisible by all nonzero elements of ⊿ belongs to the divisible part D(A) of A. (It should be noted that, while a.c. ⊿-modules are always divisible [ES], an e.c. ⊿-algebra is never divisible: see the end of §0. Moreover, an e.c. ⊿-algebra always contains torsion-free elements: see Remark 2.3.) We prove that every bounded ideal in an a.c. ⊿-algebra is principal (2.7).

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