Preprint GA 4/2005

A conjecture concerning nonlocal terms of recursion operators

By Hynek Baran and Michal Marvan

We provide examples to extend a recent conjecture concerning relation between zero curvature representations and nonlocal terms of inverse recursion operators to all recursion operators. Namely, we conjecture that nonlocal terms of recursion operators are always related to a suitable zero-curvature representation, not necessarily depending on a parameter or taking values in a semisimple algebra. In particular, the conventional pseudodifferential recursion operators correspond to abelian Lie algebras.