Graded cofinite rings of differential operators
Abstract
Description
We classify subalgebras of a ring of differential operators which are big in the sense that the extension of associated graded rings is finite. We show that these subalgebras correspond, up to automorphisms, to uniformly ramified finite morphisms. This generalizes a theorem of Levasseur-Stafford on the generators of the invariants of a Weyl algebra under a finite group.
v1: 9 pages; v2: 22 pages, completely rewritten, main theorem fixed, applications added; v3: 23 pages, references added, minor corrections
v1: 9 pages; v2: 22 pages, completely rewritten, main theorem fixed, applications added; v3: 23 pages, references added, minor corrections