fixed bug in membership test_function

the assumption made on HilbertPolynomial in the code is wrong
homalg-project · Oct 15, 2021 · e4f7774 · e4f7774
1 parent 7379063
commit e4f7774
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Showing 3 changed files with 8 additions and 7 deletions.
diff --git a/ToricSheaves/PackageInfo.g b/ToricSheaves/PackageInfo.g
@@ -10,7 +10,7 @@ SetPackageInfo( rec(
 
 PackageName := "ToricSheaves",
 Subtitle := "Toric sheaves as Serre quotients",
-Version := "2020.10-01",
+Version := "2021.02-01",
 Date := Concatenation( "01/", ~.Version{[ 6, 7 ]}, "/", ~.Version{[ 1 .. 4 ]} ),
 License := "GPL-2.0-or-later",
 

diff --git a/ToricSheaves/examples/Hirzebruch7.gi b/ToricSheaves/examples/Hirzebruch7.gi
@@ -6,14 +6,15 @@ CohH7 := CategoryOfToricSheaves( H7 );
 
 S := CoxRing( H7 );
 
-Mirr := HomalgMatrix( "[x_3*x_4,x_1*x_4,x_1*x_2,x_2*x_3]",4,1,S );
-
 gen_degs := DegreesOfGenerators( IrrelevantIdeal( H7 ) );
 
-Irrel := AsGradedLeftPresentation( Mirr );
+## A module supported on the irrelevant locus
+Mirr := AsGradedLeftPresentation( HomalgMatrix( "[x_1*x_2, x_1*x_3, x_2*x_4, x_3*x_4]", 4, 1, S ) );
+
+SheafMirr := AsSerreQuotientCategoryObject( CohH7, Mirr );
 
-SheafIrrel := AsSerreQuotientCategoryObject( CohH7, Irrel );
+Assert( 0, IsZero( SheafMirr ) );
 
-MS := AsGradedLeftPresentation( FreeLeftPresentation( 1, S ) );
+MS := GradedFreeLeftPresentation( 1, S );
 
 SheafS := AsSerreQuotientCategoryObject( CohH7, MS );
diff --git a/ToricSheaves/gap/ToricSheaves.gi b/ToricSheaves/gap/ToricSheaves.gi
@@ -36,7 +36,7 @@ InstallMethod( CategoryOfToricSheaves,
 
     presentation_category := GradedLeftPresentations( graded_ring );
 
-    if IsFree( DegreeGroup( graded_ring ) ) and ForAll( degree_matrix_as_list_list, i -> ForAll( i, j -> j >= 0 ) ) and comes_from_smooth_variety then
+    if IsFree( DegreeGroup( graded_ring ) ) and Rank( DegreeGroup( graded_ring ) ) = 1 and ForAll( degree_matrix_as_list_list, i -> ForAll( i, j -> j >= 0 ) ) and comes_from_smooth_variety then
 
         test_function := module -> IsZero( HilbertPolynomial( UnderlyingMatrixOverNonGradedRing( UnderlyingMatrix( module ) ) ) );