Toric irrelevant ideal
= Toric irrelevant ideal
{title2=$B_\Sigma$}
In the <Cox ring> $S=k[z_\rho]$, the irrelevant ideal is generated by $\prod_{\rho\notin\sigma(1)}z_\rho$ as $\sigma$ runs over maximal cones. The <Cox construction> takes the quotient of $\operatorname{Spec}S\setminus V(B_\Sigma)$ by the diagonalizable group whose character group is the divisor class group.
// Target: geometry-and-topology.bigb