X_i
The irreducible torus-invariant divisors on a normal toric variety correspond to the rays in the associated fan. In this package, the rays are ordered and indexed by the nonnegative integers. Given a normal toric variety and nonnegative integer, this method returns the corresponding irreducible torus-invariant divisor. The most convenient way to make a general torus-invariant Weil divisor is to simply write the appropriate linear combination of these torus-invariant Weil divisors.
There are three irreducible torus-invariant divisors on the projective plane.
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A torus-invariant Weil divisor is irreducible if and only if its support has a single element.
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