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NormalToricVarieties :: isEffective

isEffective -- whether a torus-invariant Weil divisor is effective

Synopsis

Description

A torus-invariant Weil divisor is effective if all the coefficients of the torus-invariant prime divisors are nonnegative.

The canonical divisor is not effective, but the anticanonical divisor is.

i1 : PP3 = projectiveSpace 3;
i2 : K = toricDivisor PP3

o2 = - PP3  - PP3  - PP3  - PP3
          0      1      2      3

o2 : ToricDivisor on PP3
i3 : isEffective K

o3 = false
i4 : isEffective(-K)

o4 = true
The torus-invariant prime divisors generate the cone of effective divisors.

See also

Ways to use isEffective :