next | previous | forward | backward | up | top | index | toc | Macaulay2 website
AssociativeAlgebras :: homogDual

homogDual -- Computes the dual of a pure homogeneous ideal

Synopsis

Description

The homogeneous dual of a pure (i.e. generators all in the same degree) ideal I in a FreeAlgebra A is generated by the orthogonal complement to the generators of I under the natural pairing on the generating subspace of A and its linear dual. Though technically the dual ideal belongs to the tensor algebra on the dual space of generators, this method returns the dual ideal in the same FreeAlgebra

If the input is a FreeAlgebraQuotient ring, the method is applied to the defining ideal of the quotient and the corresponding quotient ring is returned.

Commonly used in conjunction with quadraticClosure.

i1 : A = QQ<|x,y,z|>

o1 = A

o1 : FreeAlgebra
i2 : I = ideal{x*z-z*x, y*z, x*y^2-y^2*x, x^3*y-y*x^3}

                               2    2    3       3
o2 = ideal (x*z - z*x, y*z, x*y  - y x, x y - y*x )

o2 : Ideal of A
i3 : J = quadraticClosure I

o3 = ideal (x*z - z*x, y*z)

o3 : Ideal of A
i4 : J' = homogDual J

             2             2                   2
o4 = ideal (x , x*y, y*x, y , x*z + z*x, z*y, z )

o4 : Ideal of A

See also

Ways to use homogDual :

For the programmer

The object homogDual is a method function.