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cleanup and some extra comments
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jdebeule committed Aug 29, 2024
1 parent 3bd079e commit 461c933
Showing 1 changed file with 17 additions and 10 deletions.
27 changes: 17 additions & 10 deletions lib/recognition.gi
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#############################################################################
##
#F ClassicalForms_PossibleScalarsSesquilinear( <field>, <mat>, <frob> )
# This function returns [i0,a] such that if <mat> preserves a sesquilinear form B
# modulo scalars then the scalar lambda for which mat*B*(mat^T)^frob = lambda*B
# satisfies lambda^i0 = a.
# Very important: this function is meant to be called *only* for
# sesquilinear forms, that means, the "bar map" is the argument <frob>,
# which is the identity if we are looking for a bilinear form, and
# the involutory field automorphism in case of a hermitian form.
# This function returns [i0,a] such that if <mat> preserves a sesquilinear form B
# modulo scalars then the scalar lambda for which mat*B*(mat^T)^frob = lambda*B
# satisfies lambda^i0 = a
##
InstallGlobalFunction( ClassicalForms_PossibleScalarsSesquilinear,
function( F, M, frob )
Expand Down Expand Up @@ -81,10 +81,11 @@ InstallGlobalFunction( ClassicalForms_PossibleScalarsSesquilinear,
#############################################################################
##
#F ClassicalForms_GeneratorsWithBetterScalarsSesquilinear( grp, frob )
# Given a group <grp>, this function tries to compute a list of generators
# for <grp> that preserve a form modulo the returned scalars.
# Note that the user determines whether looking for a preserved bilinear, respectively
# hermitian form, by choosing frob to be the identiy, respectively the involutory
# field automorhipsm. This is actually just a massage of the generating set of the group.
#
##
InstallGlobalFunction( ClassicalForms_GeneratorsWithBetterScalarsSesquilinear,
function( grp, frob )
Expand Down Expand Up @@ -173,7 +174,6 @@ InstallGlobalFunction( ClassicalForms_GeneratorsWithBetterScalarsSesquilinear,

end );


#############################################################################
##
#F ClassicalForms_Signum2( <field>, <form>, <quad> )
Expand Down Expand Up @@ -295,14 +295,13 @@ InstallGlobalFunction( ClassicalForms_Signum,
return [ sgn, sqr ];
end );


#############################################################################
##
#F ClassicalForms_QuadraticForm2( <field>, <form>, <gens>, <scalars> )
## <form> is a given bilinear form, preserved by <gens> modulo <scalars>.
## This function computes a quadratic form which has <form> as polar form,
## and the quadratic form is preserved by gens (if that is all possible).
## Characteristic is two. Note that since the polar form <form> is given,
## <form> is a given bilinear form in characteristic 2, preserved by <gens>
## modulo <scalars>, this function computes a quadratic form (with <form>
## as polar form) and preserved by gens (if that is all possible).
## Note that since the polar form <form> is given, the Gram matrix of
## the quadratic form is already determined above the diagonal. So only
## the elements on the diagonal have to be computed.
##
Expand Down Expand Up @@ -388,6 +387,8 @@ InstallGlobalFunction( ClassicalForms_QuadraticForm2,
#############################################################################
##
#F ClassicalForms_QuadraticForm( <field>, <form> )
## This function should become obsolete, since forms has built in constructors
## for this.
##
InstallGlobalFunction( ClassicalForms_QuadraticForm,
function( field, form )
Expand All @@ -409,6 +410,12 @@ InstallGlobalFunction( ClassicalForms_QuadraticForm,
return H;
end );

#############################################################################
##
#F DualFrobeniusGModule( <module>, <frob>)
## Helper function for ClassicalForms_InvariantForms and
## ClassicalForms_InvariantFormFrobenius
##
InstallGlobalFunction( DualFrobeniusGModule,
function(module,frob)
#make sure frob is involution.
Expand Down

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