A Dichotomy for GK dimensions of simple modules over simple differential   rings
  The Gelfand--Kirillov dimension has gained importance since its introduction as an tool in the study of non-commutative infinite dimensional algebras and their modules. In this paper we show a dichotomy for the Gelfand--Kirillov dimension of simple modules over certain simple rings of differential operators. 
Ashish Gupta and Arnab Dey Sarkar
math.RA