PolynomialReduce

PolynomialReduce[poly,{poly1,poly2,},{x1,x2,}]

yields a list representing a reduction of poly in terms of the polyi. The list has the form {{a1,a2,},b}, where b is minimal and a1 poly1+a2 poly2++b is exactly poly.

Details and Options

  • The polynomial b has the property that none of its terms are divisible by leading terms of any of the polyi.
  • If the polyi form a Gröbner basis, then this property uniquely determines the remainder obtained from PolynomialReduce.
  • The following options can be given, as for GroebnerBasis:
  • MonomialOrderLexicographicthe criterion used for ordering monomials
    CoefficientDomainRationalsthe types of objects assumed to be coefficients
    Modulus0the modulus for numerical coefficients

Examples

open allclose all

Basic Examples  (1)

Reduce a polynomial f with respect to a list of polynomials p:

f is a linear combination of polynomials p and a remainder term r:

Scope  (1)

Reduce a polynomial modulo a list of polynomials that is not a Gröbner basis:

The remainder is not zero, even though f belongs to the ideal generated by polys:

When f belongs to the ideal generated by polys, the remainder modulo gb must be zero:

Options  (4)

CoefficientDomain  (1)

By default, PolynomialReduce works over the field of rational functions of parameters:

Compute the Gröbner basis of polys over the field of rational functions :

Reduce poly modulo gb1 over the field of rational functions :

Compute the Gröbner basis and reduce poly over the integers:

Compute the Gröbner basis and reduce poly over the rationals:

Compute the Gröbner basis and reduce poly using approximate arithmetic:

The precision used is chosen automatically, based on the precision of the Gröbner basis:

Modulus  (1)

Compute a Gröbner basis and reduce a polynomial over the integers modulo 7:

MonomialOrder  (1)

By default, PolynomialReduce uses the Lexicographic monomial order:

Any MonomialOrder allowed by GroebnerBasis can be used:

Tolerance  (1)

Compute approximate quotients:

With the default zero tolerance, d does not divide p:

Increase the tolerance to obtain an approximate quotient and a zero remainder:

Applications  (3)

Test whether polynomials belong to the ideal generated by a set of polynomials:

The remainder is zero, hence f belongs to the ideal generated by polys:

The remainder is not zero, hence g does not belong to the ideal generated by polys:

Replace variables in a polynomial using equations relating old and new variables:

The remainder gives a representation of poly in terms of a and b:

This proves correctness of the representation:

Compute the representation of a polynomial in an algebra :

Introduce tag variables and order them last in the monomial ordering:

Since the remainder is in , this shows that :

Check the result:

Properties & Relations  (3)

Reduce a polynomial with respect to a list of polynomials:

f is equal to the linear combination of polys with coefficients qs plus the remainder r:

A polynomial belongs to the ideal generated by a Gröbner basis iff it reduces to zero:

This shows that p1 is in the ideal {g1,g2}:

Univariate PolynomialReduce is equivalent to PolynomialQuotientRemainder:

Introduced in 1996
 (3.0)