Using S. E. Dickson’s
characterization of a torsion class, a class of modules closed under taking factors
extensions and arbitrary direct sum, we study torsion classes closed under taking
submodules and arbitrary direct products. We show that these classes are in
one-to-one correspondence with idempotent two sided ideals of the ring.
Finally we investigate the structure of rings R for which the torsion class
𝒯0= {M|HomR(M,Q(R)) = 0, Q(R) the minimal injective for R} is closed under
taking products.