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HyperplaneArrangements :: deCone

deCone -- produce an affine arrangement from a central one

Synopsis

Description

The decone of a central arrangement at a hyperplane H=H_i or H=ker x is the affine arrangement obtained by choosing a chart in projective space with H as the hyperplane at infinity.
i1 : A := arrangement "X3"

o1 = {x , x , x , x  + x , x  + x , x  + x }
       1   2   3   1    2   1    3   2    3

o1 : Hyperplane Arrangement 
i2 : dA := deCone(A,2)

o2 = {x , x , x  + x , x  + 1, x  + 1}
       1   2   1    2   1       2

o2 : Hyperplane Arrangement 
i3 : factor poincare A

                        2
o3 = (1 + T)(1 + 5T + 7T )

o3 : Expression of class Product
i4 : poincare dA

                2
o4 = 1 + 5T + 7T

o4 : ZZ[T]

See also

Ways to use deCone :

For the programmer

The object deCone is a method function.