support(ToricDivisor) -- make the list of irreducible divisors with nonzero coefficients

Synopsis

Function: support
Usage:

support D
Inputs:
- D, a toric divisor,
Outputs:
- a list, indexing the irreducible torus-invariant divisors whose coefficient in D are nonzero

Description

The support of a torus-invariant Weil divisor is the set of irreducible torus-invariant divisors which appear with nonzero coefficients in the unique expression for this divisor. In this package, we encode this information by indexing the irreducible torus-invariantdivisors that appear with a nonzero coefficient. The indexing of the irreducible torus-invariant divisors is inherited from the indexing of the rays in the associated fan.

i1 : PP2 = toricProjectiveSpace 2;

i2 : D1 = 2*PP2_0 - 7*PP2_1 + 3*PP2_2

o2 = 2*PP2  - 7*PP2  + 3*PP2
          0        1        2

o2 : ToricDivisor on PP2

i3 : support D1

o3 = {0, 1, 2}

o3 : List

i4 : D2 = PP2_0-5*PP2_2

o4 = PP2  - 5*PP2
        0        2

o4 : ToricDivisor on PP2

i5 : support D2

o5 = {0, 2}

o5 : List

i6 : support (6*PP2_1)

o6 = {1}

o6 : List

Ways to use this method: