If $R$ is a nonzero ring with identity then I have seen the group of units denoted by $R^{\times}$ or possibly $R^*$ in some texts. In a classical ring there is a trichotomy which declares each element in $R$ is either zero, a unit, or a zero-divisor. Naturally, for a classical ring, the set of zero-divisors and $\{0\}$ is the complement of $R$ by the group of units; $\text{set of zero divisors in $R$} \cup \{0 \} = R - R^{ \times}$.
My question is simply this:
Is there a common notation for the set of zero-divisors in a ring ?
Thanks in advance for your insight.
The one I see the most is like $Z(R)$, sometimes writing $Z^*(R)$ for the ones that aren't zero.
This collides with some other usages though, notably the center of the ring and the singular ideal of a ring.
I think I've seen it as $ZD(R)$ too, somewhere.