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TateOnProducts :: productOfProjectiveSpaces

productOfProjectiveSpaces -- Cox ring of a product of projective spaces and it Koszul dual exterior algebra

Synopsis

Description

The degrees of the variables for the i-th projective space are indexed x(i,0),..,x(i,ni-1), and have degree (0..0,1,0,..0) with a 1 in the i-th place. The script also caches some values in S.TateData and E.TateData, so that S and E can subsequently find eachother and also their cohomology ring.

i1 : (S,E)=productOfProjectiveSpaces{1,2}

o1 = (S, E)

o1 : Sequence
i2 : vars S

o2 = | x_(0,0) x_(0,1) x_(1,0) x_(1,1) x_(1,2) |

             1       5
o2 : Matrix S  <--- S
i3 : vars E

o3 = | e_(0,0) e_(0,1) e_(1,0) e_(1,1) e_(1,2) |

             1       5
o3 : Matrix E  <--- E
i4 : (S,E) = productOfProjectiveSpaces({1,1},
         Variables =>{getSymbol "u",getSymbol"v"},
         CohomologyVariables =>{getSymbol "p",getSymbol "q"},
         CoefficientField => QQ)

o4 = (S, E)

o4 : Sequence
i5 : (coefficientRing S) === (coefficientRing E)

o5 = true
i6 : trim (ideal vars S)^2

             2                                   2                       
o6 = ideal (u   , u   u   , u   u   , u   u   , u   , u   u   , u   u   ,
             1,1   1,0 1,1   0,1 1,1   0,0 1,1   1,0   0,1 1,0   0,0 1,0 
     ------------------------------------------------------------------------
      2               2
     u   , u   u   , u   )
      0,1   0,0 0,1   0,0

o6 : Ideal of S
i7 : trim (ideal vars E)^2

o7 = ideal (v   v   , v   v   , v   v   , v   v   , v   v   , v   v   )
             1,0 1,1   0,1 1,1   0,0 1,1   0,1 1,0   0,0 1,0   0,0 0,1

o7 : Ideal of E
i8 : peek S.TateData

o8 = MutableHashTable{BeilinsonBundles => MutableHashTable{}}
                      CohomRing => ZZ[p, q]
                      Rings => (S, E)

Ways to use productOfProjectiveSpaces :