%0 Journal Article %T Lattice structure of torsion classes for hereditary artin algebras %A Claus Michael Ringel %J Mathematics %D 2014 %I arXiv %X Let A be a connected hereditary artin algebra. We show that the set of functorially finite torsion classes of A-modules is a lattice if and only if A is either representation-finite (thus a Dynkin algebra) or A has only two simple modules. For the case of A being the path algebra of a quiver, this result has recently been established by Iyama-Reiten-Thomas-Todorov and our proof follows closely their considerations. %U http://arxiv.org/abs/1402.1260v1