Sobolev spaces on locally compact abelian groups
  Motivated by a class of nonlinear equations of interest for string theory, we introduce Sobolev spaces on arbitrary locally compact abelian groups and we examine some of their properties. Specifically, we focus on analogs of the Sobolev embedding and Rellich- Kondrachov compactness theorems. As an application, we prove the existence of continuous solutions to a generalized euclidean bosonic string equation possed on an arbitrary compact abelian group. 
Przemys{\l}aw G\'orka and Enrique G. Reyes
math-ph hep-th math.MP