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1 Exceptional collections
 1.1 Constructors
 1.2 General Operations

1 Exceptional collections

1.1 Constructors

1.1-1 IsStrongExceptionalCollection
‣ IsStrongExceptionalCollection( object )( filter )

Returns: true or false

The GAP category of exceptional collections.

1.1-2 CreateStrongExceptionalCollection
‣ CreateStrongExceptionalCollection( full, vertices_labels, vertices_labels_latex, cache )( operation )

Returns: IsStrongExceptionalCollection

#TODO If the input is full subcategory A in some category C, generated by finite number of objects A!.Objects, then the output is the strong exceptional collection defined by these objects. If the input is a list of objects L of objects in some category C, then the output is CreateStrongExceptionalCollection( A ), where A := FullSubcategoryGeneratedByListOfObjects(C,L).

1.1-3 StrongExceptionalCollection
‣ StrongExceptionalCollection( A )( attribute )

Returns: IsStrongExceptionalCollection

If the input is full subcategory A in some category C, generated by finite number of objects A!.Objects, then the output is the strong exceptional collection defined by these objects returned as an attribute for A.

1.1-4 FullSubcategory
‣ FullSubcategory( E )( attribute )

Returns the full subcategory that is generated by the elements of the strong exceptional collection E.

1.1-5 AmbientCategory
‣ AmbientCategory( E )( attribute )

Returns the ambient category of FullSubcategory(E).

1.1-6 EndomorphismAlgebraAttr
‣ EndomorphismAlgebraAttr( E )( attribute )

Returns: a quiver algebra

Returns the endomorphism quiver algebra of the exceptional collection E.

1.1-7 EndomorphismAlgebra
‣ EndomorphismAlgebra( E )( operation )

Returns: a quiver algebra

delegates to EndomorphismAlgebraAttr(E).

1.1-8 DefiningStrongExceptionalCollection
‣ DefiningStrongExceptionalCollection( A )( attribute )

Returns: an exceptional collection

Returns the exceptional collection that defines the quiver algebra A.

1.1-9 Algebroid
‣ Algebroid( E )( attribute )

Returns: an algebroid

Returns the algebroid defined by the endomorphism quiver algebra of the exceptional collection E.

1.1-10 QuiverRows
‣ QuiverRows( E )( attribute )

Returns: a category

Returns the category of quiver rows over the endomorphism algebra of E.

1.1-11 TiltingObject
‣ TiltingObject( E )( attribute )

Returns: an object

Returns the direct sum of the objects of the exceptional collection E.

1.1-12 NumberOfObjects
‣ NumberOfObjects( E )( attribute )

Returns: IsInt

Returns the number of objects of the exceptional collection E.

1.1-13 UnderlyingObjects
‣ UnderlyingObjects( E )( attribute )

Returns: IsList

Returns a list of the objects of the exceptional collection E.

1.1-14 AdditiveClosure
‣ AdditiveClosure( E )( attribute )

Returns: an additive category

Returns the additive closure of the FullSubcategory(E).

1.1-15 CategoryOfQuiverRepresentationsOverOppositeAlgebra
‣ CategoryOfQuiverRepresentationsOverOppositeAlgebra( E )( attribute )

Returns: an abelian category

Returns the category of right quiver representations over the opposite algebra of the endomorphism algebra of the collection.

1.1-16 HomotopyCategory
‣ HomotopyCategory( E )( operation )

Returns: a category

Returns the homotopy category of the additive closure of FullSubcategory(E).

1.1-17 AdditiveClosureAsFullSubcategory
‣ AdditiveClosureAsFullSubcategory( E )( attribute )

Returns: an additive category

Returns the additive closure of the FullSubcategory(E) as an additive full subcategory in AmbientCategory(E).

1.1-18 \[\]
\[\]( E, i )( operation )

Returns: an object

Returns the i'th object in E.

1.1-19 PathsOfLengthGreaterThanOne
‣ PathsOfLengthGreaterThanOne( E, i, j )( operation )

Returns: IsList

Returns a generating set for the vector space of morphisms from E_i to E_j that can be factored along at least one object E_l in E with i+1\leq l\leq j-1.

1.1-20 PathsOfLengthOne
‣ PathsOfLengthOne( E, i, j )( operation )

Returns: IsList

Returns a basis for a complementing vector space in Hom(E_i,E_j) to the vector space generated by PathsOfLengthGreaterThanOne(E,i,j).

1.1-21 Arrows
‣ Arrows( E, i, j )( operation )

Returns: IsList

Delegates to PathsOfLengthOne(E,[i,j]).

1.1-22 AllPaths
‣ AllPaths( E, i, j )( operation )

Returns: IsList

It returns the union of PathsOfLengthOne and PathsOfLengthGreaterThanOne applied on the same arguments. In other words it returns a generating set for the vector space Hom(E_i,E_j).

1.1-23 BasisOfPaths
‣ BasisOfPaths( E, i, j )( operation )

Returns: IsList

It returns a basis for Hom(E_i,E_j) which cosists only from paths.

1.1-24 LabelsForPathsOfLengthOne
‣ LabelsForPathsOfLengthOne( E, i, j )( operation )

Returns: IsList

It returns labels for PathsOfLengthOne(E,i,j). A label for path of length one gives information about the source, target and position of the path.

1.1-25 LabelsForPathsOfLengthGreaterThanOne
‣ LabelsForPathsOfLengthGreaterThanOne( E, i, j )( operation )

Returns: a list of lists

It returns labels for PathsOfLengthGreaterThanOne(E,i,j) A label for a path of length greater than one gives information about the labels of the arrows whose composition is the path.

1.1-26 LabelsForAllPaths
‣ LabelsForAllPaths( E, i, j )( operation )

Returns: a list of lists

It returns labels for AllPaths(E,i,j).

1.1-27 LabelsForBasisOfPaths
‣ LabelsForBasisOfPaths( E, i, j )( operation )

Returns: a list of lists

It returns labels for BasisOfPaths(E,i,j).

1.2 General Operations

1.2-1 InterpretListOfMorphismsAsOneMorphismInRangeCategoryOfHomomorphismStructure
‣ InterpretListOfMorphismsAsOneMorphismInRangeCategoryOfHomomorphismStructure( A, B, L )( operation )

Returns: a morphism in range category of homomorphism structure

The arguments are two objects A, B and a list of morphisms L:=(f_i:A\to B) for i=1,\dots,n that live in a category equipped with homomorphism structure (1,H(-,-),\nu). The output is the morphism \langle \nu(f_1),\nu(f_2),\dots,\nu(f_n)\rangle:\oplus_{i=1}^n 1 \to H(A,B).

1.2-2 RandomQuiverAlgebraWhoseIndecProjectiveRepsAreStrongExceptionalCollection
‣ RandomQuiverAlgebraWhoseIndecProjectiveRepsAreStrongExceptionalCollection( F, m, n, r )( function )

Returns: a quiver path algebra

The arguments are a field F and three non-negative integers m, n and r It returns a quiver algebra with m vertices, n arrows and at most r relations; and whose indecomposable projective or injective objects define an exceptional collection.

1.2-3 RelationsBetweenMorphisms
‣ RelationsBetweenMorphisms( L )( function )

Returns: a list of ring elements

The argument is a list of morphism L in some k-linear category equipped with homomorphism structure. The output is the relations between the morphisms.

1.2-4 FullSubcategoryGeneratedByProjectiveObjects
‣ FullSubcategoryGeneratedByProjectiveObjects( cat )( attribute )

Returns: a full subcategory

The argument is an abelian category C with enouph projectives. The output the full subcategory generated by projective objects in C.

1.2-5 FullSubcategoryGeneratedByInjectiveObjects
‣ FullSubcategoryGeneratedByInjectiveObjects( cat )( attribute )

Returns: a full subcategory

The argument is an abelian category C with enouph injectives. The output the full subcategory generated by injective objects in C.

1.2-6 FullSubcategoryGeneratedByIndecProjectiveObjects
‣ FullSubcategoryGeneratedByIndecProjectiveObjects( cat )( attribute )

Returns: a full subcategory

The argument is a category of quiver representations over some finite dimensional quiver algebra or a category of functors into a matrix category of some homalg field. The output the full subcategory generated by the indecomposable projective objects.

1.2-7 FullSubcategoryGeneratedByIndecInjectiveObjects
‣ FullSubcategoryGeneratedByIndecInjectiveObjects( cat )( attribute )

Returns: a full subcategory

The argument is a category of quiver representations over some finite dimensional quiver algebra or a category of functors into a matrix category of some homalg field. The output the full subcategory generated by the indecomposable injectives objects.

1.2-8 AdditiveClosureAsFullSubcategory
‣ AdditiveClosureAsFullSubcategory( full )( attribute )

Returns: an additive full subcategory

The argument is a non-additive full subcategory full whose ambient category C is additive. The output is an additive full subcategory of C generated by all direct sums of objects in full.

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