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Quadratic Forms and Inner Products

Quadratic Forms and Inner Products

Subsections

Defining a Quadratic Form

A bilinear form may be defined on a vector space when it is constructed using the VectorSpace-constructor.

[Future release] AssignForm(V, F) : ModTupFld, AlgMatElt ->
Suppose that the vector space V is a subspace of K^((n)). Given a matrix F belonging to Mat_K(n) that defines a bilinear form on V with respect to the current basis for V, assign F as the bilinear form associated with V.

Properties of the Form

[Future release] Discriminant(Q) : AlgMatElt -> RngIntElt
The discriminant of the quadratic form defined by the symmetric matrix Q.
[Future release] Form(V) : ModTupFld -> AlgMatElt
Return the bilinear form on V as a matrix.
[Future release] FormAsMatrix(f) : AlgPolElt -> AlgMatElt
Convert the quadratic form f into a symmetric matrix.
[Future release] FormAsPolynomial(a) : AlgMatElt -> AlgPolElt
Convert the symmetric matrix a belonging to Mat_K(n) into a polynomial, where a is interpreted as the matrix of a quadratic form.
[Future release] IsSingular(F) : AlgMatElt -> BoolElt
The rank of the bilinear form defined by the form matrix F.
[Future release] Rank(F) : AlgMatElt -> RngIntElt
The rank of the quadratic form defined by the symmetric matrix F.
[Future release] WittIndex(Q) : AlgMatElt -> RngIntElt
The Witt index of the quadratic form defined by the symmetric matrix Q.

Structure of Inner Product Spaces

[Future release] IsotropicVector(V) : ModTupFld -> ModTupFldElt
An isotropic vector in V relative to the bilinear form currently defined on V.
[Future release] MaximalIsotropicSubspace(V) : ModTupFld -> ModTupFld
Construct a maximal isotropic subspace in V relative to the bilinear form currently defined on V.
[Future release] OrthogonalBasis(V) : ModTupFld -> { ModTupFldElt }
Construct an orthogonal basis for the vector space V with respect to the bilinear form currently defined on V.
[Future release] OrthogonalComplement(V, U) : ModTupFld, ModTupFld -> ModTupFld
The orthogonal complement of the subspace U in the vector space V with respect to the bilinear form currently defined on V.
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