Search results for "Hilbert function"

showing 5 items of 5 documents

A numerical property of Hilbert functions and lex segment ideals

2017

We introduce the fractal expansions, sequences of integers associated to a number. We show that these sequences characterize the Osequences and encode some information about lex segment ideals. Moreover, we introduce numerical functions called fractal functions, and we use them to solve the open problem of the classification of the Hilbert functions of any bigraded algebra.

13F20 13A15 13D40Settore MAT/02 - AlgebraBigraded algebraLex segment idealMathematics::Commutative AlgebraHilbert functionFOS: MathematicsSettore MAT/03 - GeometriaCommutative Algebra (math.AC)Mathematics - Commutative AlgebraBigraded algebra Hilbert function Lex segment idealBigraded algebra; Hilbert function; Lex segment ideal
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On the Betti numbers of three fat points in P1 × P1

2019

In these notes we introduce a numerical function which allows us to describe explicitly (and nonrecursively) the Betti numbers, and hence, the Hilbert function of a set Z of three fat points whose support is an almost complete intersection (ACI) in P1 × P1 . A nonrecursively formula for the Betti numbers and the Hilbert function of these configurations is hard to give even for the corresponding set of five points on a special support in P2 and we did not find any kind of this result in the literature. Moreover, we also give a criterion that allows us to characterize the Hilbert functions of these special set of fat points.

13F20Fat points Hilbert functions Multiprojective spaces13A15Fat pointsMathematics - Commutative Algebra13D40Mathematics - Algebraic GeometrySettore MAT/02 - AlgebraFat points; Hilbert functions; Multiprojective spacesMultiprojective spacesSettore MAT/03 - GeometriaMathematics - Algebraic Geometry; Mathematics - Algebraic Geometry; Mathematics - Commutative Algebra; 13F20 13A15 13D40 14M0514M05Hilbert functions
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Tower sets and other configurations with the Cohen-Macaulay property

2014

Abstract Some well-known arithmetically Cohen–Macaulay configurations of linear varieties in P r as k-configurations, partial intersections and star configurations are generalized by introducing tower schemes. Tower schemes are reduced schemes that are a finite union of linear varieties whose support set is a suitable finite subset of Z + c called tower set. We prove that the tower schemes are arithmetically Cohen–Macaulay and we compute their Hilbert function in terms of their support. Afterwards, since even in codimension 2 not every arithmetically Cohen–Macaulay squarefree monomial ideal is the ideal of a tower scheme, we slightly extend this notion by defining generalized tower schemes …

MonomialTower setBetti sequence; Cohen-Macaulay; Tower setCommutative Algebra (math.AC)Combinatoricssymbols.namesake13H10 14N20 13D40FOS: MathematicsMathematicsmonomial idealsHilbert series and Hilbert polynomialAlgebra and Number TheoryIdeal (set theory)Mathematics::Commutative AlgebraCohen–Macaulay propertyMonomial idealCodimensionBetti sequenceMathematics - Commutative AlgebraTower (mathematics)Arithmetically Cohen-MacaulayCohen-MacaulayPrimary decompositionSettore MAT/02 - AlgebraScheme (mathematics)Hilbert functionsymbolsSettore MAT/03 - GeometriaCohen–Macaulay property monomial ideals Hilbert function.
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Expecting the unexpected: Quantifying the persistence of unexpected hypersurfaces

2021

If $X \subset \mathbb P^n$ is a reduced subscheme, we say that $X$ admits an unexpected hypersurface of degree $t$ for multiplicity $m$ if the imposition of having multiplicity $m$ at a general point $P$ fails to impose the expected number of conditions on the linear system of hypersurfaces of degree $t$ containing $X$. Conditions which either guarantee the occurrence of unexpected hypersurfaces, or which ensure that they cannot occur, are not well understand. We introduce new methods for studying unexpectedness, such as the use of generic initial ideals and partial elimination ideals to clarify when it can and when it cannot occur. We also exhibit algebraic and geometric properties of $X$ …

Pure mathematicsGeneral MathematicsComplete intersectionVector bundleAlgebraic geometrysymbols.namesakeMathematics - Algebraic GeometryAV-sequence; Complete intersection; Generic initial ideal; Hilbert function; Partial elimination ideal; Unexpected hypersurfaceUnexpected hypersurfaceFOS: MathematicsAlgebraic numberAV-sequenceAlgebraic Geometry (math.AG)Complete intersectionGeneric initial idealMathematicsHilbert series and Hilbert polynomialSequencePartial elimination idealSettore MAT/02 - AlgebraHypersurfaceHyperplanePrimary: 14C20 13D40 14Q10 14M10 Secondary: 14M05 14M07 13E10Hilbert functionsymbolsSettore MAT/03 - GeometriaAV-sequence Complete intersection Generic initial ideal Hilbert function Partial elimination ideal Unexpected hypersurface
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THE HILBERT FUNCTION OF BIGRADED ALGEBRAS IN k[P1x P1]

2020

We classify the Hilbert functions of bigraded algebras in k[x1, x2, y1, y2] by introducing a numerical function called a Ferrers function.

Settore MAT/02 - AlgebraHilbert function multigraded algebra numerical functionSettore MAT/03 - Geometria
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