degeneracyLocus(ZZ,AbstractSheaf,AbstractSheaf)

Synopsis

• Function: degeneracyLocus

• Usage:

  degeneracyLocus(k,B,A)

• Inputs:
  • k, an integer,
  • B, an abstract sheaf,
  • A, an abstract sheaf,
• Outputs:
  • an abstract variety, the locus where the rank of a generic map from A to B is at most k

Description

i1 : X = base(5, Bundle => (A,3,a), Bundle => (B,3,b))

o1 = X

o1 : an abstract variety of dimension 5

i2 : Z = degeneracyLocus(2,B,A)

o2 = Z

o2 : an abstract variety of dimension 4

i3 : Z/X

o3 = a variety map

o3 : a map to X from Z

i4 : (Z/X)_* 1

o4 = - a  + b
        1    1

o4 : QQ[a ..b ]
         1   3