  Let Q be a finite quiver without oriented cycles, and let k be an
algebraically closed field. The main result in this paper is that there is a
natural bijection between the elements in the associated Coxeter group W_Q and
the cofinite additive quotient-closed subcategories of the category of finite
dimensional right modules over kQ. We prove this correspondence by linking
these subcategories to certain ideals in the preprojective algebra associated
to Q, which are also indexed by elements of W_Q.
