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10 The coframe of Zariski closed subsets in a projective variety
 10.1 GAP Categories
 10.2 Attributes
 10.3 Constructors

10 The coframe of Zariski closed subsets in a projective variety

10.1 GAP Categories

10.1-1 IsZariskiCoframeOfAProjectiveVariety
‣ IsZariskiCoframeOfAProjectiveVariety( object )( filter )

Returns: true or false

The GAP category of Zariski coframes of a projective variety.

10.1-2 IsObjectInZariskiCoframeOfAProjectiveVariety
‣ IsObjectInZariskiCoframeOfAProjectiveVariety( object )( filter )

Returns: true or false

The GAP category of objects in a Zariski coframe of a projective variety.

10.1-3 IsMorphismInZariskiCoframeOfAProjectiveVariety
‣ IsMorphismInZariskiCoframeOfAProjectiveVariety( morphism )( filter )

Returns: true or false

The GAP category of morphisms in a Zariski coframe of a projective variety.

10.2 Attributes

10.2-1 UnderlyingClosedSubsetOfSpec
‣ UnderlyingClosedSubsetOfSpec( arg )( attribute )

10.3 Constructors

10.3-1 ZariskiCoframeOfProj
‣ ZariskiCoframeOfProj( R )( attribute )

Returns: a CAP category

Construct the Zariski coframe of closed sets in a projective variety defined as the vanishing loci of (radical) ideals of a homalg ring R.

10.3-2 ClosedSubsetOfProj
‣ ClosedSubsetOfProj( mat )( operation )
‣ ClosedSubsetOfProj( str, R )( operation )
‣ ClosedSubsetOfProjByListOfColumns( L )( operation )

Returns: a CAP object

Construct a Zariski closed subset (as an object in the Zariski coframe of closed subsets a projective variety) from the homogeneous matrix mat. The result is the projective support of the module-theoretic cokernel \(M\) of the matrix mat viewed as a morphism in the Freyd category of the associated category of graded rows, i.e., the result is the projective vanishing locus of the (homogeneous) annihilator of \(M\).

10.3-3 ClosedSubsetOfProjByRadicalColumn
‣ ClosedSubsetOfProjByRadicalColumn( I )( operation )
‣ ClosedSubsetOfProjByRadicalColumn( str, R )( operation )

ClosedSubsetOfProjByRadicalColumn assumes that the image is a radical ideal.

10.3-4 ClosedSubsetOfProjByStandardColumn
‣ ClosedSubsetOfProjByStandardColumn( I )( operation )
‣ ClosedSubsetOfProjByStandardColumn( str, R )( operation )

ClosedSubsetOfProjByStandardColumn assumes that the image is a radical ideal given by some sort of a "standard" basis.

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