Quelle SerreQuotientsByCospans.gi Sprache: unbekannt

# SPDX-License-Identifier: GPL-2.0-or-later
# GeneralizedMorphismsForCAP: Implementations of generalized morphisms for the CAP project
#
# Implementations
#

#############################################
##
## Installation method
##
#############################################

BindGlobal( "CAP_INTERNAL_INSTALL_OPERATIONS_FOR_SERRE_QUOTIENT_BY_COSPANS",

  function( category )
    local membership_function;

    membership_function := SubcategoryMembershipTestFunctionForSerreQuotient( category );

    ## Equalities

    AddIsCongruentForMorphisms( category,

      function( cat, morphism1, morphism2 )
        local underlying_generalized_category, underlying_general, new_morphism_aid, new_general, sum_general,
              sum_associated, sum_image;

        underlying_generalized_category := UnderlyingGeneralizedMorphismCategory( cat );

        underlying_general := UnderlyingGeneralizedMorphism( morphism2 );

        new_general := AdditiveInverse( underlying_generalized_category, underlying_general );

        sum_general := AdditionForMorphisms( underlying_generalized_category, UnderlyingGeneralizedMorphism( morphism1 ), new_general );

        sum_associated := AssociatedMorphism( sum_general );

        sum_image := ImageObject( underlying_generalized_category, sum_associated );

        return membership_function( sum_image );

    end );

    AddIsEqualForObjects( category,

      function( cat, obj1, obj2 )

        return IsEqualForObjects( UnderlyingHonestCategory( cat ), UnderlyingHonestObject( obj1 ), UnderlyingHonestObject( obj2 ) );

    end );

    ## Is Zero

    AddIsZeroForObjects( category,

      function( cat, obj )

        return membership_function( UnderlyingHonestObject( obj ) );

    end );

    ## PreCompose

    AddPreCompose( category,

      function( cat, morphism1, morphism2 )
        local underlying_generalized_category, composition;

        underlying_generalized_category := UnderlyingGeneralizedMorphismCategory( cat );

        composition := PreCompose( underlying_generalized_category,
                                   UnderlyingGeneralizedMorphism( morphism1 ),
                                   UnderlyingGeneralizedMorphism( morphism2 ) );

        return SerreQuotientCategoryByCospansMorphism( cat, composition );

    end );

    ## IdentityMorphism

    AddIdentityMorphism( category,

      function( cat, object )

        return AsSerreQuotientCategoryByCospansMorphism( cat,
                                                         IdentityMorphism( UnderlyingHonestCategory( cat ),
                                                         UnderlyingHonestObject( object ) ) );

    end );

    ## Addition for morphisms

    AddAdditionForMorphisms( category,

      function( cat, morphism1, morphism2 )
        local underlying_generalized_category, sum;

        underlying_generalized_category := UnderlyingGeneralizedMorphismCategory( cat );

        sum := AdditionForMorphisms( underlying_generalized_category,
                                     UnderlyingGeneralizedMorphism( morphism1 ),
                                     UnderlyingGeneralizedMorphism( morphism2 ) );

        return SerreQuotientCategoryByCospansMorphism( cat, sum );

    end );

    ## IsZeroForMorphisms
    ## Can be derived, but there might be a faster solution
#     AddIsZeroForMorphisms( category,
#
#       function( cat, morphism )
#         local honest_category, associated, image;
#
#         honest_category := UnderlyingHonestCategory( cat );
#
#         associated := AssociatedMorphism( UnderlyingGeneralizedMorphism( morphism ) );
#
#         image := ImageObject( honest_category, associated );
#
#         return membership_function( image );
#
#     end );

    ## Additive inverse for morphisms (works without normalization)

    AddAdditiveInverseForMorphisms( category,

      function( cat, morphism )
        local underlying_generalized_category, new_general;

        underlying_generalized_category := UnderlyingGeneralizedMorphismCategory( cat );

        new_general := AdditiveInverseForMorphisms( underlying_generalized_category, UnderlyingGeneralizedMorphism( morphism ) );

        return SerreQuotientCategoryByCospansMorphism( cat, new_general );

    end );

    ## Zero morphism

    AddZeroMorphism( category,

      function( cat, source, range )
        local underlying_generalized_category, new_general;

        underlying_generalized_category := UnderlyingGeneralizedMorphismCategory( cat );

        new_general := ZeroMorphism( underlying_generalized_category,
                                     UnderlyingGeneralizedObject( source ),
                                     UnderlyingGeneralizedObject( range ) );

        return SerreQuotientCategoryByCospansMorphism( cat, new_general );

    end );

    ## Zero object

    AddZeroObject( category,

      function( cat )
        local generalized_zero;

        generalized_zero := ZeroObject( UnderlyingHonestCategory( cat ) );

        return AsSerreQuotientCategoryByCospansObject( cat, generalized_zero );

    end );

    ## direct sum

    AddDirectSum( category,

      function( cat, obj_list )
        local honest_category, honest_list, honest_sum;

        honest_category := UnderlyingHonestCategory( cat );

        honest_list := List( obj_list, UnderlyingHonestObject );

        honest_sum := DirectSum( cat, honest_list );

        return AsSerreQuotientCategoryByCospansObject( cat, honest_sum );

    end );

    AddProjectionInFactorOfDirectSumWithGivenDirectSum( category,

      function( cat, product_object, component_number, direct_sum_object )
        local honest_category, underlying_objects, underlying_direct_sum, honest_projection;

        honest_category := UnderlyingHonestCategory( cat );

        underlying_objects := List( product_object, UnderlyingHonestObject );

        underlying_direct_sum := UnderlyingHonestObject( direct_sum_object );

        honest_projection := ProjectionInFactorOfDirectSumWithGivenDirectSum( honest_category,
                                                                              underlying_objects,
                                                                              component_number,
                                                                              underlying_direct_sum );

        return AsSerreQuotientCategoryByCospansMorphism( cat, honest_projection );

    end );

    AddInjectionOfCofactorOfDirectSumWithGivenDirectSum( category,

      function( cat, object_product_list, injection_number, direct_sum_object )
        local honest_category, underlying_objects, underlying_direct_sum, honest_injection;

        honest_category := UnderlyingHonestCategory( cat );

        underlying_objects := List( object_product_list, UnderlyingHonestObject );

        underlying_direct_sum := UnderlyingHonestObject( direct_sum_object );

        honest_injection := AddInjectionOfCofactorOfDirectSumWithGivenDirectSum( honest_category,
                                                                                 underlying_objects,
                                                                                 injection_number,
                                                                                 underlying_direct_sum );

        return AsSerreQuotientCategoryByCospansMorphism( cat, honest_injection );

    end );

    AddUniversalMorphismIntoDirectSum( category,

      function( cat, diagram, test_object, morphism_list )
        local honest_category, generalized_list, arrow_list, reversedarrow_list, new_arrow, new_reversed_arrow, object_list;

        honest_category := UnderlyingHonestCategory( cat );

        generalized_list := List( morphism_list, UnderlyingGeneralizedMorphism );

        arrow_list := List( generalized_list, Arrow );

        new_arrow := UniversalMorphismIntoDirectSum( honest_category, List( arrow_list, Range ), arrow_list );

        reversedarrow_list := List( generalized_list, ReversedArrow );

        new_reversed_arrow := DirectSumFunctorial( honest_category, reversedarrow_list );

        return SerreQuotientCategoryByCospansMorphism( cat, new_arrow, new_reversed_arrow );

    end );

    ## Needs work
    AddUniversalMorphismFromDirectSum( category,

      function( cat, diagram, test_object, morphism_list )
        local honest_category, generalized_list, arrow_list, reversedarrow_list, new_arrow, new_reversed_arrow, object_list;

        honest_category := UnderlyingHonestCategory( cat );

        generalized_list := List( morphism_list, UnderlyingGeneralizedMorphism );

        generalized_list := CommonCoastriction( generalized_list );

        arrow_list := List( generalized_list, Arrow );

        new_arrow := UniversalMorphismFromDirectSum( honest_category, List( diagram, UnderlyingHonestObject ), arrow_list );

        new_reversed_arrow := ReversedArrow( generalized_list[ 1 ] );

        return SerreQuotientCategoryByCospansMorphism( cat, new_arrow, new_reversed_arrow );

    end );

    ## Kernel

    AddKernelEmbedding( category,

      function( cat, morphism )
        local honest_category, underlying_general, kernel_mor;

        honest_category := UnderlyingHonestCategory( cat );

        underlying_general := UnderlyingGeneralizedMorphism( morphism );

        kernel_mor := KernelEmbedding( honest_category, Arrow( underlying_general ) );

        return AsSerreQuotientCategoryByCospansMorphism( cat, kernel_mor );

    end );

    AddLiftAlongMonomorphism( category,

      function( cat, monomorphism, test_morphism )
        local underlying_generalized_category, inverse_of_mono, composition;

        underlying_generalized_category := UnderlyingGeneralizedMorphismCategory( cat );

        inverse_of_mono := PseudoInverse( UnderlyingGeneralizedMorphism( monomorphism ) );

        composition := PreCompose( underlying_generalized_category, UnderlyingGeneralizedMorphism( test_morphism ), inverse_of_mono );

        return SerreQuotientCategoryByCospansMorphism( cat, composition );

    end );

    ## Cokernel

    AddCokernelProjection( category,

      function( cat, morphism )
        local honest_category, underlying_general, cokernel_mor, triple;

        honest_category := UnderlyingHonestCategory( cat );

        underlying_general := UnderlyingGeneralizedMorphism( morphism );

        triple := DomainAssociatedMorphismCodomainTriple( underlying_general );

        cokernel_mor := CokernelProjection( honest_category, triple[ 2 ] );

        return AsSerreQuotientCategoryByCospansMorphism( cat, PreCompose( honest_category, triple[ 3 ], cokernel_mor ) );

    end );

    AddColiftAlongEpimorphism( category,

      function( cat, epimorphism, test_morphism )
        local underlying_generalized_category, inverse_of_epi, composition;

        underlying_generalized_category := UnderlyingGeneralizedMorphismCategory( cat );

        inverse_of_epi := PseudoInverse( UnderlyingGeneralizedMorphism( epimorphism ) );

        composition := PreCompose( underlying_generalized_category, inverse_of_epi, UnderlyingGeneralizedMorphism( test_morphism ) );

        return SerreQuotientCategoryByCospansMorphism( cat, composition );

    end );

end );

#############################################
##
## Constructor
##
#############################################

InstallMethod( SerreQuotientCategoryByCospans,
               [ IsCapCategory, IsFunction ],

  function( category, test_function )
    local name;

    name := NameFunction( test_function );

    return SerreQuotientCategoryByCospans( category, test_function, Concatenation( "test function with name: ", name ) );

end );

InstallMethodWithCacheFromObject( SerreQuotientCategoryByCospans,
                                  [ IsCapCategory, IsFunction, IsString ],

  function( category, test_function, function_name )
    local serre_category, gen_category, name, preconditions, i;

    if not IsFinalized( category ) then

        Error( "category must be finalized" );
        return;

    fi;

    preconditions := [ "IsEqualForObjects",
                       "ImageObject",
                       "AdditiveInverseForMorphisms",
                       "IdentityMorphism",
                       "ZeroMorphism",
                       "DirectSum",
                       "ProjectionInFactorOfDirectSumWithGivenDirectSum",
                       "InjectionOfCofactorOfDirectSumWithGivenDirectSum",
                       "UniversalMorphismFromDirectSum",
                       "UniversalMorphismIntoDirectSum",
                       "DirectSumFunctorialWithGivenDirectSums",
                       "KernelEmbedding",
                       "CokernelProjection" ];

    for i in preconditions do

        if not CanCompute( category, i ) then

            Error( Concatenation( "category must be able to compute ", i ) );
            return;

        fi;

    od;

    name := Name( category );

    name := Concatenation( "The Serre quotient category of ", name, " by ", function_name );

    serre_category := CreateCapCategoryWithDataTypes(
                              name,
                              IsSerreQuotientCategory,
                              IsSerreQuotientCategoryByCospansObject,
                              IsSerreQuotientCategoryByCospansMorphism and HasUnderlyingGeneralizedMorphism,
                              IsCapCategoryTwoCell,
                              fail,
                              fail,
                              fail );

    serre_category!.predicate_logic := category!.predicate_logic;

    SetFilterObj( serre_category, WasCreatedAsSerreQuotientCategoryByCospans );

    SetUnderlyingHonestCategory( serre_category, category );

    SetUnderlyingGeneralizedMorphismCategory( serre_category, GeneralizedMorphismCategoryByCospans( category ) );

    SetSubcategoryMembershipTestFunctionForSerreQuotient( serre_category, test_function );

    SetIsAbelianCategory( serre_category, true );

    CAP_INTERNAL_INSTALL_OPERATIONS_FOR_SERRE_QUOTIENT_BY_COSPANS( serre_category );

    CAP_INTERNAL_INSTALL_OPERATIONS_FOR_SERRE_QUOTIENT( serre_category );

    Finalize( serre_category );

    return serre_category;

end );

InstallMethodWithCacheFromObject( AsSerreQuotientCategoryByCospansObject,
                                  [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans, IsCapCategoryObject ],

  function( serre_category, object )
    local honest_category, serre_object;

    honest_category := UnderlyingHonestCategory( serre_category );

    if not IsIdenticalObj( honest_category, CapCategory( object ) ) then

        Error( "object does not belong to underlying honest category of serre quotient" );

    fi;

    serre_object := CreateCapCategoryObjectWithAttributes( serre_category,
                                                           UnderlyingHonestObject, object,
                                                           UnderlyingGeneralizedObject, GeneralizedMorphismByCospansObject( object ) );

    if HasSpecializedObjectFilterForSerreQuotients( serre_category ) then

        SetFilterObj( serre_object, SpecializedObjectFilterForSerreQuotients( serre_category ) );

    fi;

    return serre_object;

end );

InstallMethodWithCacheFromObject( SerreQuotientCategoryByCospansMorphism,
                                  [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans, IsGeneralizedMorphismByCospan ],

  function( serre_category, gen_morphism )
    local honest_category, serre_morphism;

    if not IsIdenticalObj( UnderlyingGeneralizedMorphismCategory( serre_category ), CapCategory( gen_morphism ) ) then

        Error( "generalized morphism has wrong category" );

    fi;

    serre_morphism := CreateCapCategoryMorphismWithAttributes( serre_category,
                                                               AsSerreQuotientCategoryByCospansObject( serre_category, UnderlyingHonestObject( Source( gen_morphism ) ) ),
                                                               AsSerreQuotientCategoryByCospansObject( serre_category, UnderlyingHonestObject( Range( gen_morphism ) ) ),
                                                               UnderlyingGeneralizedMorphism, gen_morphism );

    if HasSpecializedMorphismFilterForSerreQuotients( serre_category ) then

        SetFilterObj( serre_morphism, SpecializedMorphismFilterForSerreQuotients( serre_category ) );

    fi;

    return serre_morphism;

end );

InstallMethod( SerreQuotientCategoryByCospansMorphism,
               [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans, IsCapCategoryMorphism, IsCapCategoryMorphism, IsCapCategoryMorphism ],

  function( serre_category, source_aid, associated, range_aid )

    return SerreQuotientCategoryByCospansMorphism( serre_category, GeneralizedMorphismByCospan( source_aid, associated, range_aid ) );

end );

InstallMethod( SerreQuotientCategoryByCospansMorphismWithSourceAid,
               [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans, IsCapCategoryMorphism, IsCapCategoryMorphism ],

  function( serre_category, source_aid, associated )

    return SerreQuotientCategoryByCospansMorphism( serre_category, GeneralizedMorphismByCospanWithSourceAid( source_aid, associated ) );

end );

InstallMethod( SerreQuotientCategoryByCospansMorphism,
               [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans, IsCapCategoryMorphism, IsCapCategoryMorphism ],

  function( serre_category, reversed_arrow, arrow )

    return SerreQuotientCategoryByCospansMorphism( serre_category, GeneralizedMorphismByCospan( reversed_arrow, arrow ) );

end );

InstallMethodWithCacheFromObject( AsSerreQuotientCategoryByCospansMorphism,
                                  [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans, IsCapCategoryMorphism ],

  function( serre_category, associated )

    return SerreQuotientCategoryByCospansMorphism( serre_category, AsGeneralizedMorphismByCospan( associated ) );

end );

#############################################
##
## Compatibility layer
##
#############################################

InstallMethod( AsSerreQuotientCategoryObject,
               [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans, IsCapCategoryObject ],

  AsSerreQuotientCategoryByCospansObject );

InstallMethod( AsSerreQuotientCategoryMorphism,
               [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans, IsCapCategoryMorphism ],

  AsSerreQuotientCategoryByCospansMorphism );

InstallMethod( SerreQuotientCategoryMorphism,
               [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans, IsGeneralizedMorphismByCospan ],

  SerreQuotientCategoryByCospansMorphism );

InstallMethod( SerreQuotientCategoryMorphism,
               [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans, IsCapCategoryMorphism, IsCapCategoryMorphism, IsCapCategoryMorphism ],

  SerreQuotientCategoryByCospansMorphism );

InstallMethod( SerreQuotientCategoryMorphism,
               [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans, IsCapCategoryMorphism, IsCapCategoryMorphism ],

  SerreQuotientCategoryByCospansMorphism );

InstallMethod( SerreQuotientCategoryMorphismWithRangeAid,
               [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans, IsCapCategoryMorphism, IsCapCategoryMorphism ],

  SerreQuotientCategoryByCospansMorphism );

InstallMethod( SerreQuotientCategoryMorphismWithSourceAid,
               [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans, IsCapCategoryMorphism, IsCapCategoryMorphism ],

  SerreQuotientCategoryByCospansMorphismWithSourceAid );

#############################################
##
## Functor
##
#############################################

InstallMethod( CanonicalProjection,
               [ IsCapCategory and WasCreatedAsSerreQuotientCategoryByCospans ],

  function( category )
    local underlying_honest, functor;

    underlying_honest := UnderlyingHonestCategory( category );

    functor := CapFunctor( Concatenation( "Localization functor of ", Name( category ) ), underlying_honest, category );

    AddObjectFunction( functor,

        i -> AsSerreQuotientCategoryByCospansObject( category, i ) );

    AddMorphismFunction( functor,

      function( new_source, morphism, new_range )

        return AsSerreQuotientCategoryByCospansMorphism( category, morphism );

    end );

    return functor;

end );

Quelle SerreQuotientsByCospans.gi Sprache: unbekannt

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