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<Chapter Label="chap:demo"> <Heading>A demo session with <Package>simpcomp</Package></Heading>
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This chapter contains the transcript of a demo session with <Package>simpcomp</Package> that is intended to give an insight into what things can be done with this package.<P/>
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Of course this only scratches the surface of the functions provided by <Package>simpcomp</Package>. See Chapters <Ref Chap="chap:polyhedralcomplex"/> through <Ref Chap="chap:misc"/> for further functions provided by <Package>simpcomp</Package>.
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<Section Label="sec:DemoCreatingCompl">
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<Heading>Creating a <C>SCSimplicialComplex</C> object</Heading>
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Simplicial complex objects can either be created from a facet list (complex <C>c1</C> below), orbit representatives together with a permutation group (complex <C>c2</C>) or difference cycles (complex <C>c3</C>, see Section <Ref Chap="sec:FromScratch"/>), from a function generating triangulations of standard complexes (complex <C>c4</C>, see Section <Ref Chap="sec:Standard"/>) or from a function constructing infinite series for combinatorial (pseudo)manifolds (complexes <C>c5</C>, <C>c6</C>, <C>c7</C>, see Section <Ref Chap="sec:Series"/> and the function prefix <C>SCSeries...</C>). There are also functions creating new simplicial complexes from old, see Section <Ref Chap="sec:generateFromOld" />, which will be described in the next sections.
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<Log>
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gap> #first run functionality test on simpcomp
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gap> SCRunTest();
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+ test simpcomp package, version 2.1.7
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+ GAP4stones: 69988
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true
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gap> #all ok
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gap> c1:=SCFromFacets([[1,2],[2,3],[3,1]]);
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[SimplicialComplex
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Properties known: Dim, Facets, Name, VertexLabels.
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Name="unnamed complex 1"
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Dim=1
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/SimplicialComplex]
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gap> G:=Group([(2,12,11,6,8,3)(4,7,10)(5,9),(1,11,6,4,5,3,10,8,9,7,2,12)]);
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Group([ (2,12,11,6,8,3)(4,7,10)(5,9), (1,11,6,4,5,3,10,8,9,7,2,12) ])
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gap> StructureDescription(G);
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"S4 x S3"
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gap> Size(G);
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144
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gap> c2:=SCFromGenerators(G,[[1,2,3]]);;
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gap> c2.IsManifold;
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true
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gap> SCLibDetermineTopologicalType(c2);
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[SimplicialComplex
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Properties known: AutomorphismGroup, AutomorphismGroupSize,
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AutomorphismGroupStructure, AutomorphismGroupTransitivity,\
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Boundary, Dim, Faces, Facets, Generators, HasBoundary,
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IsManifold, IsPM, Name, TopologicalType, VertexLabels,
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Vertices.
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Name="complex from generators under group S4 x S3"
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Dim=2
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AutomorphismGroupSize=144
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AutomorphismGroupStructure="S4 x S3"
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AutomorphismGroupTransitivity=1
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HasBoundary=false
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IsPM=true
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TopologicalType="T^2"
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/SimplicialComplex]
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gap> c3:=SCFromDifferenceCycles([[1,1,6],[3,3,2]]);
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[SimplicialComplex
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Properties known: Dim, Facets, Name, VertexLabels.
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Name="complex from diffcycles [ [ 1, 1, 6 ], [ 3, 3, 2 ] ]"
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Dim=2
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/SimplicialComplex]
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gap> c4:=SCBdSimplex(2);
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[SimplicialComplex
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Properties known: AutomorphismGroup, AutomorphismGroupOrder,
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AutomorphismGroupStructure, AutomorphismGroupTransitivity,
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Chi, Dim, F, Facets, Generators, HasBounday, Homology,
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IsConnected, IsStronglyConnected, Name, TopologicalType,
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VertexLabels.
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Name="S^1_3"
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Dim=1
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AutomorphismGroupStructure="S3"
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AutomorphismGroupTransitivity=3
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Chi=0
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F=[ 3, 3 ]
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Homology=[ [ 0, [ ] ], [ 1, [ ] ] ]
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IsConnected=true
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IsStronglyConnected=true
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TopologicalType="S^1"
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/SimplicialComplex]
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gap> c5:=SCSeriesCSTSurface(2,16);;
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gap> SCLibDetermineTopologicalType(c5);
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[SimplicialComplex
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Properties known: Boundary, Dim, Faces, Facets, HasBoundary, IsPM, Name,
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TopologicalType, VertexLabels.
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Name="cst surface S_{(2,16)} = { (2:2:12),(6:6:4) }"
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Dim=2
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HasBoundary=false
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IsPM=true
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TopologicalType="T^2 U T^2"
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/SimplicialComplex]
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gap> c6:=SCSeriesD2n(22);;
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gap> c6.Homology;
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[ [ 0, [ ] ], [ 1, [ ] ], [ 0, [ 2 ] ], [ 0, [ ] ] ]
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gap> c6.F;
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[ 44, 264, 440, 220 ]
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gap> SCSeriesAGL(17);
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[ AGL(1,17), [ [ 1, 2, 4, 8, 16 ] ] ]
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gap> c7:=SCFromGenerators(last[1],last[2]);;
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gap> c7.AutomorphismGroupTransitivity;
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2
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</Log>
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</Section>
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<Section Label="sec:DemoWorkingCompl">
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<Heading>Working with a <C>SCSimplicialComplex</C> object</Heading>
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As described in Section <Ref Sect="sec:AcessSC" /> there are two several ways of accessing an object of type <C>SCSimplicialComplex</C>. An example for the two equivalent ways is given below. The preference will be given to the object oriented notation in this demo session.
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The code listed below
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<Log>
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gap> c:=SCBdSimplex(3);; # create a simplicial complex object
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gap> SCFVector(c);
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[ 4, 6, 4 ]
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gap> SCSkel(c,0);
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[ [ 1 ], [ 2 ], [ 3 ], [ 4 ] ]
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</Log>
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is equivalent to
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<Log>
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gap> c:=SCBdSimplex(3);; # create a simplicial complex object
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gap> c.F;
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[ 4, 6, 4 ]
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gap> c.Skel(0);
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[ [ 1 ], [ 2 ], [ 3 ], [ 4 ] ]
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</Log>
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</Section>
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<Section Label="sec:DemoPropsCompl">
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<Heading>Calculating properties of a <C>SCSimplicialComplex</C> object</Heading>
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<Package>simpcomp</Package> provides a variety of functions for calculating properties of simplicial complexes, see Section <Ref Chap="sec:glprops" />. All these properties are only calculated once and stored in the <C>SCSimplicialComplex</C> object.
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<Log>
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gap> c1.F;
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[ 3, 3 ]
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gap> c1.FaceLattice;
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[ [ [ 1 ], [ 2 ], [ 3 ] ], [ [ 1, 2 ], [ 1, 3 ], [ 2, 3 ] ] ]
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gap> c1.AutomorphismGroup;
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S3
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gap> c1.Generators;
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[ [ [ 1, 2 ], 3 ] ]
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gap> c3.Facets;
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[ [ 1, 2, 3 ], [ 1, 2, 8 ], [ 1, 3, 6 ], [ 1, 4, 6 ], [ 1, 4, 7 ],
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[ 1, 7, 8 ], [ 2, 3, 4 ], [ 2, 4, 7 ], [ 2, 5, 7 ], [ 2, 5, 8 ],
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[ 3, 4, 5 ], [ 3, 5, 8 ], [ 3, 6, 8 ], [ 4, 5, 6 ], [ 5, 6, 7 ],
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[ 6, 7, 8 ] ]
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gap> c3.F;
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[ 8, 24, 16 ]
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gap> c3.G;
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[ 4 ]
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gap> c3.H;
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[ 5, 11, -1 ]
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gap> c3.ASDet;
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186624
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gap> c3.Chi;
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0
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gap> c3.Generators;
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[ [ [ 1, 2, 3 ], 16 ] ]
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gap> c3.HasBoundary;
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false
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gap> c3.IsConnected;
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true
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gap> c3.IsCentrallySymmetric;
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true
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gap> c3.Vertices;
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[ 1, 2, 3, 4, 5, 6, 7, 8 ]
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gap> c3.ConnectedComponents;
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[ [SimplicialComplex
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Properties known: Dim, Facets, Name, VertexLabels.
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Name="Connected component #1 of complex from diffcycles [ [ 1, 1, 6 ], [ \
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3, 3, 2 ] ]"
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Dim=2
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/SimplicialComplex] ]
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gap> c3.UnknownProperty;
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#I SCPropertyObject: unhandled property 'UnknownProperty'. Handled properties\
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are [ "Equivalent", "IsKStackedSphere", "IsManifold", "IsMovable", "Move",
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"Moves", "RMoves", "ReduceAsSubcomplex", "Reduce", "ReduceEx", "Copy",
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"Recalc", "ASDet", "AutomorphismGroup", "AutomorphismGroupInternal",
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"Boundary", "ConnectedComponents", "Dim", "DualGraph", "Chi", "F",
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"FaceLattice", "FaceLatticeEx", "Faces", "FacesEx", "Facets", "FacetsEx",
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"FpBetti", "FundamentalGroup", "G", "Generators", "GeneratorsEx", "H",
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"HasBoundary", "HasInterior", "Homology", "Incidences", "IncidencesEx",
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"Interior", "IsCentrallySymmetric", "IsConnected", "IsEmpty",
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"IsEulerianManifold", "IsHomologySphere", "IsInKd", "IsKNeighborly",
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"IsOrientable", "IsPM", "IsPure", "IsShellable", "IsStronglyConnected",
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"MinimalNonFaces", "MinimalNonFacesEx", "Name", "Neighborliness",
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"Orientation", "Skel", "SkelEx", "SpanningTree",
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"StronglyConnectedComponents", "Vertices", "VerticesEx",
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"BoundaryOperatorMatrix", "HomologyBasis", "HomologyBasisAsSimplices",
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"HomologyInternal", "CoboundaryOperatorMatrix", "Cohomology",
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"CohomologyBasis", "CohomologyBasisAsSimplices", "CupProduct",
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"IntersectionForm", "IntersectionFormParity",
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"IntersectionFormDimensionality", "Load", "Save", "ExportPolymake",
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"ExportLatexTable", "ExportJavaView", "LabelMax", "LabelMin", "Labels",
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"Relabel", "RelabelStandard", "RelabelTransposition", "Rename",
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"SortComplex", "UnlabelFace", "AlexanderDual", "CollapseGreedy", "Cone",
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"DeletedJoin", "Difference", "HandleAddition", "Intersection",
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"IsIsomorphic", "IsSubcomplex", "Isomorphism", "IsomorphismEx", "Join",
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"Link", "Links", "Neighbors", "NeighborsEx", "Shelling", "ShellingExt",
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"Shellings", "Span", "Star", "Stars", "Suspension", "Union",
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"VertexIdentification", "Wedge", "DetermineTopologicalType", "Dim",
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"Facets", "VertexLabels", "Name", "Vertices", "IsConnected",
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"ConnectedComponents" ].
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fail
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</Log>
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</Section>
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<Section Label="sec:DemoNewCompl">
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<Heading>Creating new complexes from a <C>SCSimplicialComplex</C> object</Heading>
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As already mentioned, there is the possibility to generate new objects of type <C>SCSimplicialComplex</C> from existing ones using standard constructions. The functions used in this section are described in more detail in Section <Ref Chap="sec:generateFromOld"/>.
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<Log>
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gap> d:=c3+c3;
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[SimplicialComplex
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Properties known: Dim, Facets, Name, VertexLabels, Vertices.
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Name="complex from diffcycles [ [ 1, 1, 6 ], [ 3, 3, 2 ] ]#+-complex from dif\
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fcycles [ [ 1, 1, 6 ], [ 3, 3, 2 ] ]"
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Dim=2
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/SimplicialComplex]
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gap> SCRename(d,"T^2#T^2");
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true
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gap> SCLink(d,1);
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[SimplicialComplex
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Properties known: Dim, Facets, Name, VertexLabels.
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Name="lk(1) in T^2#T^2"
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Dim=1
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/SimplicialComplex]
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gap> SCStar(d,[1,2]);
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[SimplicialComplex
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Properties known: Dim, Facets, Name, VertexLabels.
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Name="star([ 1, 2 ]) in T^2#T^2"
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Dim=2
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/SimplicialComplex]
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gap> SCRename(c3,"T^2");
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true
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gap> SCConnectedProduct(c3,4);
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[SimplicialComplex
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Properties known: Dim, Facets, Name, VertexLabels, Vertices.
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Name="T^2#+-T^2#+-T^2#+-T^2"
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Dim=2
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/SimplicialComplex]
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gap> SCCartesianProduct(c4,c4);
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[SimplicialComplex
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Properties known: Dim, Facets, Name, TopologicalType, VertexLabels.
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Name="S^1_3xS^1_3"
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Dim=2
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TopologicalType="S^1xS^1"
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/SimplicialComplex]
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gap> SCCartesianPower(c4,3);
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[SimplicialComplex
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Properties known: Dim, Facets, Name, TopologicalType, VertexLabels.
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Name="(S^1_3)^3"
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Dim=3
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TopologicalType="(S^1)^3"
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/SimplicialComplex]
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</Log>
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</Section>
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<Section Label="sec:DemoHom">
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<Heading>Homology related calculations</Heading>
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<Package>simpcomp</Package> relies on the GAP package homology <Cite Key="Dumas04Homology" /> for its homology computations but provides further (co-)homology related functions, see Chapter <Ref Chap="chap:homology"/>.
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<Log>
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gap> s2s2:=SCCartesianProduct(SCBdSimplex(3),SCBdSimplex(3));
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[SimplicialComplex
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Properties known: Dim, Facets, Name, TopologicalType, VertexLabels.
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Name="S^2_4xS^2_4"
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Dim=4
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TopologicalType="S^2xS^2"
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/SimplicialComplex]
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gap> SCHomology(s2s2);
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[ [ 0, [ ] ], [ 0, [ ] ], [ 2, [ ] ], [ 0, [ ] ], [ 1, [ ] ] ]
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gap> SCHomologyInternal(s2s2);
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[ [ 0, [ ] ], [ 0, [ ] ], [ 2, [ ] ], [ 0, [ ] ], [ 1, [ ] ] ]
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gap> SCHomologyBasis(s2s2,2);
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[ [ 1, [ [ 1, 70 ], [ -1, 12 ], [ 1, 2 ], [ -1, 1 ] ] ],
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[ 1, [ [ 1, 143 ], [ -1, 51 ], [ 1, 29 ], [ -1, 25 ] ] ] ]
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gap> SCHomologyBasisAsSimplices(s2s2,2);
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[ [ 1,
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[ [ 1, [ 2, 3, 4 ] ], [ -1, [ 1, 3, 4 ] ], [ 1, [ 1, 2, 4 ] ], [ -1, [ 1
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, 2, 3 ] ] ] ],
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[ 1, [ [ 1, [ 5, 9, 13 ] ], [ -1, [ 1, 9, 13 ] ], [ 1, [ 1, 5, 13 ] ],
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[ -1, [ 1, 5, 9 ] ] ] ] ]
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gap> SCCohomologyBasis(s2s2,2);
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[ [ 1,
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[ [ 1, 122 ], [ 1, 115 ], [ 1, 112 ], [ 1, 111 ], [ 1, 93 ], [ 1, 90 ],
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[ 1, 89 ], [ 1, 84 ], [ 1, 83 ], [ 1, 82 ], [ 1, 46 ], [ 1, 43 ],
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[ 1, 42 ], [ 1, 37 ], [ 1, 36 ], [ 1, 35 ], [ 1, 28 ], [ 1, 27 ],
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[ 1, 26 ], [ 1, 25 ] ] ],
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[ 1, [ [ 1, 213 ], [ 1, 201 ], [ 1, 192 ], [ 1, 189 ], [ 1, 159 ],
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[ 1, 150 ], [ 1, 147 ], [ 1, 131 ], [ 1, 128 ], [ 1, 125 ],
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[ 1, 67 ], [ 1, 58 ], [ 1, 55 ], [ 1, 39 ], [ 1, 36 ], [ 1, 33 ],
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[ 1, 10 ], [ 1, 7 ], [ 1, 4 ], [ 1, 1 ] ] ] ]
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gap> SCCohomologyBasisAsSimplices(s2s2,2);
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[ [ 1, [ [ 1, [ 4, 8, 12 ] ], [ 1, [ 3, 8, 12 ] ], [ 1, [ 3, 7, 12 ] ],
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[ 1, [ 3, 7, 11 ] ], [ 1, [ 2, 8, 12 ] ], [ 1, [ 2, 7, 12 ] ],
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[ 1, [ 2, 7, 11 ] ], [ 1, [ 2, 6, 12 ] ], [ 1, [ 2, 6, 11 ] ],
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[ 1, [ 2, 6, 10 ] ], [ 1, [ 1, 8, 12 ] ], [ 1, [ 1, 7, 12 ] ],
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[ 1, [ 1, 7, 11 ] ], [ 1, [ 1, 6, 12 ] ], [ 1, [ 1, 6, 11 ] ],
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[ 1, [ 1, 6, 10 ] ], [ 1, [ 1, 5, 12 ] ], [ 1, [ 1, 5, 11 ] ],
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[ 1, [ 1, 5, 10 ] ], [ 1, [ 1, 5, 9 ] ] ] ],
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[ 1, [ [ 1, [ 13, 14, 15 ] ], [ 1, [ 9, 14, 15 ] ], [ 1, [ 9, 10, 15 ] ],
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[ 1, [ 9, 10, 11 ] ], [ 1, [ 5, 14, 15 ] ], [ 1, [ 5, 10, 15 ] ],
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[ 1, [ 5, 10, 11 ] ], [ 1, [ 5, 6, 15 ] ], [ 1, [ 5, 6, 11 ] ],
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[ 1, [ 5, 6, 7 ] ], [ 1, [ 1, 14, 15 ] ], [ 1, [ 1, 10, 15 ] ],
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[ 1, [ 1, 10, 11 ] ], [ 1, [ 1, 6, 15 ] ], [ 1, [ 1, 6, 11 ] ],
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[ 1, [ 1, 6, 7 ] ], [ 1, [ 1, 2, 15 ] ], [ 1, [ 1, 2, 11 ] ],
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[ 1, [ 1, 2, 7 ] ], [ 1, [ 1, 2, 3 ] ] ] ] ]
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gap> PrintArray(SCIntersectionForm(s2s2));
350
[ [ 0, 1 ],
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[ 1, 0 ] ]
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gap> c:=s2s2+s2s2;
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[SimplicialComplex
354
355
Properties known: Dim, Facets, Name, VertexLabels, Vertices.
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357
Name="S^2_4xS^2_4#+-S^2_4xS^2_4"
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Dim=4
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/SimplicialComplex]
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gap> PrintArray(SCIntersectionForm(c));
362
[ [ 0, -1, 0, 0 ],
363
[ -1, 0, 0, 0 ],
364
[ 0, 0, 0, -1 ],
365
[ 0, 0, -1, 0 ] ]
366
</Log>
367
368
</Section>
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<Section Label="sec:DemoBist">
371
<Heading>Bistellar flips</Heading>
372
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For a more detailed description of functions related to bistellar flips as well as a very short introduction into the topic, see Chapter <Ref Chap="chap:bistellar"/>.
374
<Log>
375
gap> beta4:=SCBdCrossPolytope(4);;
376
gap> s3:=SCBdSimplex(4);;
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gap> SCEquivalent(beta4,s3);
378
#I round 0, move: [ [ 2, 6, 7 ], [ 3, 4 ] ]
379
[ 8, 25, 34, 17 ]
380
#I round 1, move: [ [ 2, 7 ], [ 3, 4, 5 ] ]
381
[ 8, 24, 32, 16 ]
382
#I round 2, move: [ [ 2, 5 ], [ 3, 4, 8 ] ]
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[ 8, 23, 30, 15 ]
384
#I round 3, move: [ [ 2 ], [ 3, 4, 6, 8 ] ]
385
[ 7, 19, 24, 12 ]
386
#I round 4, move: [ [ 6, 8 ], [ 1, 3, 4 ] ]
387
[ 7, 18, 22, 11 ]
388
#I round 5, move: [ [ 8 ], [ 1, 3, 4, 5 ] ]
389
[ 6, 14, 16, 8 ]
390
#I round 6, move: [ [ 5 ], [ 1, 3, 4, 7 ] ]
391
[ 5, 10, 10, 5 ]
392
#I SCReduceComplexEx: complexes are bistellarly equivalent.
393
true
394
gap> SCBistellarOptions.WriteLevel;
395
0
396
gap> SCBistellarOptions.WriteLevel:=1;
397
1
398
gap> SCEquivalent(beta4,s3);
399
#I SCLibInit: made directory "~/PATH" for user library.
400
#I SCIntFunc.SCLibInit: index not found -- trying to reconstruct it.
401
#I SCLibUpdate: rebuilding index for ~/PATH.
402
#I SCLibUpdate: rebuilding index done.
403
404
#I round 0, move: [ [ 2, 4, 6 ], [ 7, 8 ] ]
405
[ 8, 25, 34, 17 ]
406
#I round 1, move: [ [ 2, 4 ], [ 5, 7, 8 ] ]
407
[ 8, 24, 32, 16 ]
408
#I round 2, move: [ [ 4, 5 ], [ 1, 7, 8 ] ]
409
[ 8, 23, 30, 15 ]
410
#I round 3, move: [ [ 4 ], [ 1, 6, 7, 8 ] ]
411
[ 7, 19, 24, 12 ]
412
#I SCLibAdd: saving complex to file "complex_ReducedComplex_7_vertices_3_2009\
413
-10-27_11-40-00.sc".
414
#I round 4, move: [ [ 2, 6 ], [ 3, 7, 8 ] ]
415
[ 7, 18, 22, 11 ]
416
#I round 5, move: [ [ 2 ], [ 3, 5, 7, 8 ] ]
417
[ 6, 14, 16, 8 ]
418
#I SCLibAdd: saving complex to file "complex_ReducedComplex_6_vertices_5_2009\
419
-10-27_11-40-00.sc".
420
#I round 6, move: [ [ 5 ], [ 1, 3, 7, 8 ] ]
421
[ 5, 10, 10, 5 ]
422
#I SCLibAdd: saving complex to file "complex_ReducedComplex_5_vertices_6_2009\
423
-10-27_11-40-00.sc".
424
#I SCLibAdd: saving complex to file "complex_ReducedComplex_5_vertices_7_2009\
425
-10-27_11-40-00.sc".
426
#I SCReduceComplexEx: complexes are bistellarly equivalent.
427
true
428
gap> myLib:=SCLibInit("~/PATH"); # copy path from above
429
[Simplicial complex library. Properties:
430
CalculateIndexAttributes=true
431
Number of complexes in library=4
432
IndexAttributes=[ "Name", "Date", "Dim", "F", "G", "H", "Chi", "Homology" ]
433
Loaded=true
434
Path="/home/spreerjn/reducedComplexes/2009-10-27_11-40-00/"
435
]
436
gap> s3:=myLib.Load(3);
437
[SimplicialComplex
438
439
Properties known: Chi, Date, Dim, F, Faces, Facets, G, H, Homology,
440
IsConnected, Name, VertexLabels.
441
442
Name="ReducedComplex_5_vertices_6"
443
Dim=3
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Chi=0
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F=[ 5, 10, 10, 5 ]
446
G=[ 0, 0 ]
447
H=[ 1, 1, 1, 1 ]
448
Homology=[ [ 0, [ ] ], [ 0, [ ] ], [ 0, [ ] ], [ 1, [ ] ] ]
449
IsConnected=true
450
451
/SimplicialComplex]
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gap> s3:=myLib.Load(2);
453
[SimplicialComplex
454
455
Properties known: Chi, Date, Dim, F, Faces, Facets, G, H, Homology,
456
IsConnected, Name, VertexLabels.
457
458
Name="ReducedComplex_6_vertices_5"
459
Dim=3
460
Chi=0
461
F=[ 6, 14, 16, 8 ]
462
G=[ 1, 0 ]
463
H=[ 2, 2, 2, 1 ]
464
Homology=[ [ 0, [ ] ], [ 0, [ ] ], [ 0, [ ] ], [ 1, [ ] ] ]
465
IsConnected=true
466
467
/SimplicialComplex]
468
gap> t2:=SCCartesianProduct(SCBdSimplex(2),SCBdSimplex(2));;
469
gap> t2.F;
470
[ 9, 27, 18 ]
471
gap> SCBistellarOptions.WriteLevel:=0;
472
0
473
gap> SCBistellarOptions.LogLevel:=0;
474
0
475
gap> mint2:=SCReduceComplex(t2);
476
[ true, [SimplicialComplex
477
478
Properties known: Dim, Facets, Name, VertexLabels.
479
480
Name="unnamed complex 85"
481
Dim=2
482
483
/SimplicialComplex], 32 ]
484
</Log>
485
</Section>
486
487
<Section Label="sec:DemoBlowups">
488
<Heading>Simplicial blowups</Heading>
489
490
For a more detailed description of functions related to simplicial blowups see Chapter <Ref Chap="chap:blowups"/>.
491
<Log>
492
gap> list:=SCLib.SearchByName("Kummer");
493
[ [ 7493, "4-dimensional Kummer variety (VT)" ] ]
494
gap> c:=SCLib.Load(7493);
495
[SimplicialComplex
496
497
Properties known: AltshulerSteinberg, AutomorphismGroup,
498
AutomorphismGroupSize, AutomorphismGroupStructure,
499
AutomorphismGroupTransitivity,
500
ConnectedComponents, Date, Dim, DualGraph,
501
EulerCharacteristic, FacetsEx, GVector,
502
GeneratorsEx, HVector, HasBoundary, HasInterior,
503
Homology, Interior, IsCentrallySymmetric,
504
IsConnected, IsEulerianManifold, IsManifold,
505
IsOrientable, IsPseudoManifold, IsPure,
506
IsStronglyConnected, MinimalNonFacesEx, Name,
507
Neighborliness, NumFaces[], Orientation,
508
SkelExs[], Vertices.
509
510
Name="4-dimensional Kummer variety (VT)"
511
Dim=4
512
AltshulerSteinberg=45137758519296000000000000
513
AutomorphismGroupSize=1920
514
AutomorphismGroupStructure="((C2 x C2 x C2 x C2) : A5) : C2"
515
AutomorphismGroupTransitivity=1
516
EulerCharacteristic=8
517
GVector=[ 10, 55, 60 ]
518
HVector=[ 11, 66, 126, -19, 7 ]
519
HasBoundary=false
520
HasInterior=true
521
Homology=[ [0, [ ] ], [0, [ ] ], [6, [2,2,2,2,2] ], [0, [ ] ], [1, [ ] ] ]
522
IsCentrallySymmetric=false
523
IsConnected=true
524
IsEulerianManifold=true
525
IsOrientable=true
526
IsPseudoManifold=true
527
IsPure=true
528
IsStronglyConnected=true
529
Neighborliness=2
530
531
/SimplicialComplex]
532
gap> lk:=SCLink(c,1);
533
[SimplicialComplex
534
535
Properties known: Dim, FacetsEx, Name, Vertices.
536
537
Name="lk([ 1 ]) in 4-dimensional Kummer variety (VT)"
538
Dim=3
539
540
/SimplicialComplex]
541
gap> SCHomology(lk);
542
[ [ 0, [ ] ], [ 0, [ 2 ] ], [ 0, [ ] ], [ 1, [ ] ] ]
543
gap> SCLibDetermineTopologicalType(lk);
544
[ 45, 113, 2426, 2502, 7470 ]
545
gap> d:=SCLib.Load(45);;
546
gap> d.Name;
547
"RP^3"
548
gap> SCEquivalent(lk,d);
549
#I SCReduceComplexEx: complexes are bistellarly equivalent.
550
true
551
gap> e:=SCBlowup(c,1);
552
#I SCBlowup: checking if singularity is a combinatorial manifold...
553
#I SCBlowup: ...true
554
#I SCBlowup: checking type of singularity...
555
#I SCReduceComplexEx: complexes are bistellarly equivalent.
556
#I SCBlowup: ...ordinary double point (supported type).
557
#I SCBlowup: starting blowup...
558
#I SCBlowup: map boundaries...
559
#I SCBlowup: boundaries not isomorphic, initializing bistellar moves...
560
#I SCBlowup: found complex with smaller boundary: f = [ 15, 74, 118, 59 ].
561
#I SCBlowup: found complex with smaller boundary: f = [ 14, 70, 112, 56 ].
562
#I SCBlowup: found complex with smaller boundary: f = [ 14, 69, 110, 55 ].
563
#I SCBlowup: found complex with smaller boundary: f = [ 14, 68, 108, 54 ].
564
#I SCBlowup: found complex with smaller boundary: f = [ 13, 64, 102, 51 ].
565
#I SCBlowup: found complex with smaller boundary: f = [ 13, 63, 100, 50 ].
566
#I SCBlowup: found complex with smaller boundary: f = [ 13, 62, 98, 49 ].
567
#I SCBlowup: found complex with smaller boundary: f = [ 12, 58, 92, 46 ].
568
#I SCBlowup: found complex with smaller boundary: f = [ 12, 57, 90, 45 ].
569
#I SCBlowup: found complex with smaller boundary: f = [ 12, 56, 88, 44 ].
570
#I SCBlowup: found complex with smaller boundary: f = [ 11, 52, 82, 41 ].
571
#I SCBlowup: found complex with smaller boundary: f = [ 11, 51, 80, 40 ].
572
#I SCBlowup: found complex with isomorphic boundaries.
573
#I SCBlowup: ...boundaries mapped succesfully.
574
#I SCBlowup: build complex...
575
#I SCBlowup: ...done.
576
#I SCBlowup: ...blowup completed.
577
#I SCBlowup: You may now want to reduce the complex via 'SCReduceComplex'.
578
[SimplicialComplex
579
580
Properties known: Dim, FacetsEx, Name, Vertices.
581
582
Name="unnamed complex 6315 \ star([ 1 ]) in unnamed complex 6315 cup unnamed\
583
complex 6319 cup unnamed complex 6317"
584
Dim=4
585
586
/SimplicialComplex]
587
gap> SCHomology(c);
588
[ [ 0, [ ] ], [ 0, [ ] ], [ 6, [ 2, 2, 2, 2, 2 ] ], [ 0, [ ] ], [ 1, [ ] ] ]
589
gap> SCHomology(e);
590
[ [ 0, [ ] ], [ 0, [ ] ], [ 7, [ 2, 2, 2, 2 ] ], [ 0, [ ] ], [ 1, [ ] ] ]
591
</Log>
592
</Section>
593
594
595
<Section Label="sec:DemoDiscreteNormalSurface">
596
<Heading>Discrete normal surfaces and slicings</Heading>
597
598
For a more detailed description of functions related to discrete normal surfaces and slicings see the Sections <Ref Chap="sec:NormSurfTheory"/> and <Ref Chap="sec:MorseTheory"/>.
599
<Log>
600
601
gap> # the boundary of the cyclic 4-polytope with 6 vertices
602
gap> c:=SCBdCyclicPolytope(4,6);
603
[SimplicialComplex
604
605
Properties known: Dim, EulerCharacteristic, FacetsEx, HasBoundary, Homology,\
606
IsConnected, IsStronglyConnected, Name, NumFaces[], TopologicalType, Vertices.
607
608
Name="Bd(C_4(6))"
609
Dim=3
610
EulerCharacteristic=0
611
HasBoundary=false
612
Homology=[ [ 0, [ ] ], [ 0, [ ] ], [ 0, [ ] ], [ 1, [ ] ] ]
613
IsConnected=true
614
IsStronglyConnected=true
615
TopologicalType="S^3"
616
617
/SimplicialComplex]
618
gap> # slicing in between the odd and the even vertex labels, a polyhedral torus
619
gap> sl:=SCSlicing(c,[[2,4,6],[1,3,5]]);
620
[NormalSurface
621
622
Properties known: ConnectedComponents, Dim, EulerCharacteristic, FVector,\
623
FacetsEx, Genus, IsConnected, IsOrientable, NSTriangulation, Name,\
624
TopologicalType, Vertices.
625
626
Name="slicing [ [ 2, 4, 6 ], [ 1, 3, 5 ] ] of Bd(C_4(6))"
627
Dim=2
628
FVector=[ 9, 18, 0, 9 ]
629
EulerCharacteristic=0
630
IsOrientable=true
631
TopologicalType="T^2"
632
633
/NormalSurface]
634
gap> sl.Homology;
635
[ [ 0, [ ] ], [ 2, [ ] ], [ 1, [ ] ] ]
636
gap> sl.Genus;
637
1
638
gap> sl.F; # the slicing constists of 9 quadrilaterals and 0 triangles
639
[ 9, 18, 0, 9 ]
640
gap> PrintArray(sl.Facets);
641
[ [ [ 2, 1 ], [ 2, 3 ], [ 4, 1 ], [ 4, 3 ] ],
642
[ [ 2, 1 ], [ 2, 3 ], [ 6, 1 ], [ 6, 3 ] ],
643
[ [ 2, 1 ], [ 2, 5 ], [ 4, 1 ], [ 4, 5 ] ],
644
[ [ 2, 1 ], [ 2, 5 ], [ 6, 1 ], [ 6, 5 ] ],
645
[ [ 2, 3 ], [ 2, 5 ], [ 4, 3 ], [ 4, 5 ] ],
646
[ [ 2, 3 ], [ 2, 5 ], [ 6, 3 ], [ 6, 5 ] ],
647
[ [ 4, 1 ], [ 4, 3 ], [ 6, 1 ], [ 6, 3 ] ],
648
[ [ 4, 1 ], [ 4, 5 ], [ 6, 1 ], [ 6, 5 ] ],
649
[ [ 4, 3 ], [ 4, 5 ], [ 6, 3 ], [ 6, 5 ] ] ]
650
</Log></Section>
651
652
Further example computations can be found in the slides of various talks about <Package>simpcomp</Package>, available from the <Package>simpcomp</Package> homepage (<C>https://github.com/simpcomp-team/simpcomp</C>), and in Appendix A of <Cite Key="Spreer10Diss"/>.
653
</Chapter>
654
655
656