In: Advanced Math
Let R be a ring (not necessarily commutative), and let X denote the set of two-sided ideals
of R.
(i) Show that X is a poset with respect to to set-theoretic inclusion, ⊂.
(ii) Show that with respect to the operations I ∩ J and I + J (candidates for meet and join;
remember that I+J consists of the set of sums, {i + j} where i ∈ I and j ∈ J) respectively,
X is a lattice.
(iii) Give an example of a commutative ring for which the corresponding X is not a Boolean
algebra, and one for which it is.