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Resultants :: Resultants

Resultants -- A package for computing resultants.

Description

Resultants is a package for elimination theory, emphasizing universal formulas, in particular, resultant computations.

The package contains an implementation for computing determinant of free graded complexes, called detComplex, with several derived methods: listDetComplex, mapsComplex, and minorsComplex. This provides a method for producing universal formulas for any family of schemes, just by combining the resolution(Ideal) method with detComplex. In Section 2 determinants of free resolutions are treated, as well as a few examples. We recommend to see [Dem84, Jou95, GKZ94, Bus06] for more details on determinants of complexes in elimination theory.

The package also provides methods for computing matrices and formulas for different resultants applicable on different families of polynomials, such as the Macaulay resultant (macRes) for generic homogeneous polynomials; residual resultant (ciRes, cm2Res) for generic polynomials having a non empty base locus scheme; determinantal resultant (detRes) for generic polynomial matrices of a given generic rank. Those resultants and their implementation are reviewed in Section 3 and for the theory behind the author can refer to [Jou91, Cha93, GKZ94, Jou95, Jou97, CLO98, BEM01, Bus01b, Bus06, Bus04].

The goal of this package is to provide universal formulas for elimination. The main advantage of this approach consists in the fact that we can provide formulas for any family of polynomials just by taking determinant to a free resolution. A direct consequence of a universal formula is that it is preserved by base change, this is, in particular, it commutes with specialization. A deep study of universal formulas for the image of a map of schemes can be seen in [EH00].

Bibliography:

[BBD12] Nicolás Botbol, Laurent Busé and Manuel Dubinsky. PDF. Package for elimination theory in Macaulay2 (2012).

[BEM00] Laurent Busé, Mohamed Elkadi and Bernard Mourrain, Generalized resultants over unirational algebraic varieties, J. Symbolic Comput. 29 (2000), no. 4-5, 515–526.

[BEM01] Laurent Busé, Mohamed Elkadi and Bernard Mourrain, Resultant over the residual of a complete intersection, Journal of Pure and Applied Algebra 164 (2001), no. 1-2, 35–57.

[Bus01a] Laurent Busé, Residual resultant over the projective plane and the implicitization problem, Internation Symposium on Symbolic and Algebraic Computing (ISSAC), ACM, (2001). Please, see the errata.pdf attached file., pp. 48–55.

[Bus01b] Laurent Busé, Étude du resultant sur une variété algébrique. phd thesis. (2001)

[Bus04] Laurent Busé, Resultants of determinantal varieties, J.Pure Appl. Algebra193 (2004), no.1-3, 71–97.

[Bus06] Laurent Busé, Elimination theory in codimension one and applications, (2006).

[Cha93] Marc Chardin, The resultant via a Koszul complex, Computational algebraic geometry (1992), Progr. Math, vol. 109, Birkhäuser Boston, Boston, MA, pp. 29–39.

[CLO98] David Cox, John Little and Donal O’Shea, Using algebraic geometry, Graduate Texts in Mathematics, vol. 185, Springer-Verlag, New York, (1998).

[Dem94] Michel Demazure, Une définition constructive du resultant, Centre de Mathématiques de l’Ecole Polytechnique 2 (1984), no. Notes informelles du calcul formel 1984-1994, 0–23.

[EH00] David Eisenbud and Joe Harris, The geometry of schemes., Graduate Texts in Mathematics. 197. New York, NY: Springer. x, 294 p., (2000).

[Eis95] David Eisenbud, Commutative algebra, With a view toward algebraic geometry. Graduate Texts in Mathematics, vol. 150, Springer-Verlag, New York, (1995).

[GKZ94] Israel M. Gel′fand, Mikhail M. Kapranov and Andrei V. Zelevinsky, Discriminants, resultants, and multidimensional determinants, (1994). Mathematics: Theory & Applications, Birkh ̈auser Boston Inc, Boston, MA.

[Jou91] Jean-Pierre Jouanolou, Le formalisme du résultant, Adv. Math 90 (1991), no. 2, 117–263.

[Jou95] Jean-Pierre Jouanolou, Aspects invariants de l’élimination, vol. 114, 1995, pp. 1–174.

[Jou97] Jean-Pierre Jouanolou, Formes d’inertie et résultant: un formulaire, Adv. Math. 126 (1997), no. 2, 119–250.

[Mac02] Francis S. Macaulay, Some formulae in elimination, Proc. London Math. Soc. 33 (1902), no. 1, 3–27.

[Mou02] Bernard Mourrain, Enumeration problems in Geometry, Robotics and Vision, Prog. in Math. 143 (1996), 285–306.

Authors

Version

This documentation describes version 1.4 of Resultants.

Source code

The source code from which this documentation is derived is in the file Resultants.m2.

Exports

  • Functions and commands
    • bezoutianMatrix -- returns a matrix associated to generalized resultants
    • ciRes -- returns a matrix corresponding to the residual resultant over a complete intersection
    • ciResDeg -- compute a regularity index and partial degrees of the residual resultant over a complete intersection
    • ciResDegGH -- compute a regularity index used for the residual resultant over a complete intersection
    • cm2Res -- returns a matrix corresponding to the residual resultant over a Cohen-Macaulay codimension 2 base locus
    • degHomPolMap -- given a subset of variables 'var' of the polynomial ring R, it returns the base of monomials on these variables, and the matrix of coefficients of a morphism of free modules f:R(d1)+...+R(dn)->R_d with respect to these variables
    • degMap -- This function returns the matrix of coefficients of the morphism of free modules 'm' in the variables 'var'
    • detComplex -- This function calculates the determinant of a graded ChainComplex with respect to a subset of the variables of the polynomial ring in a fixed degree.
    • detComplexNum -- This function calculates the determinant of a graded ChainComplex with respect to a subset of the variables of the polynomial ring in a fixed degree.
    • detRes -- returns a matrix corresponding to the residual resultant over a Cohen-Macaulay codimension 2 base locus
    • detResDeg -- compute a regularity index and partial degrees of the determinantal resultant
    • listDetComplex -- This function calculates the list with the determinants of some minors of the maps of a graded ChainComplex with respect to a subset of the variables of the polynomial ring in a fixed degree.
    • listDetComplexNum -- This function calculates the list with the determinants of some minors of the maps of a graded ChainComplex with respect to a subset of the variables of the polynomial ring in a fixed degree.
    • macaulayFormula -- returns two matrices such that the ratio of their determinants is the Macaulay resultant
    • macRes -- returns a matrix associated to the Macaulay resultant
    • mapsComplex -- This function calculates the maps of a graded ChainComplex with respect to a subset of the variables of the polynomial ring in a fixed degree.
    • maxCol -- Returns a submatrix form by a maximal set of linear independent columns.
    • maxColNum -- Returns a submatrix form by a maximal set of linear independent columns by random evaluation.
    • maxMinor -- Returns a maximal minor of the matrix of full rank.
    • maxMinorNum -- Returns a maximal minor of the matrix of full rank by random evaluation.
    • minorsComplex -- This function calculates some minors of the maps of a graded ChainComplex with respect to a subset of the variables of the polynomial ring in a fixed degree. The choice of the minors is according to the construction of the determinant of a complex
    • minorsComplexNum -- This function calculates some minors of the maps of a graded ChainComplex with respect to a subset of the variables of the polynomial ring in a fixed degree.
    • rankNum -- computes the rank of a matrix by random evaluation.