Commutative Algebra

For an ideal $I$ in a ring $R$, recall that $D(I)\subseteq \operatorname{Spec}(R)$ denotes the set of prime ideals $\wp$ of $R$ not containing $I$, i.e. primes $\wp$ such that $(R-\wp)\cap I\neq \emptyset$. Alternatively, you can think of $D(I)$ as the set of primes $\wp$ for which there exists an element $f\in I$ that is nonzero modulo $\wp$.