Given a commutative ring $R$, we can define a divisibility relation by $a|b$ on the elements of $R$ iff there exists $c \in R$ such that $b = ca$. What are the properties of this relation in general? Is it, like the case of the integers a lattice?
I know for certain cases (e.g. integral domains) this is indeed the case, but what about more general rings? In particular, I am interested in cases where the nilradical of $R$ is non-trivial. In particular, I would like to know in what instances can we say in general that such a preorder is a meet semilattice.
The divisibility poset of a ring $R$ is a lattice iff every pair of elements has a gcd and a lcm.
This does not happen in every commutative ring.
For instance, in the ring $\mathbb Z[\sqrt{-5}]$ there is no gcd for $6$ and $2(1+\sqrt{-5})$ (see this).
A class of rings that have this property is GCD domains, which generalize UFDs.