Exact and semiclassical approach to a class of singular integral   operators arising in fluid mechanics and quantum field theory
  A class of singular integral operators, encompassing two physically relevant cases arising in perturbative QCD and in classical fluid dynamics, is presented and analyzed. It is shown that three special values of the parameters allow for an exact eigenfunction expansion; these can be associated to Riemannian symmetric spaces of rank one with positive, negative or vanishing curvature. For all other cases an accurate semiclassical approximation is derived, based on the identification of the operators with a peculiar Schroedinger-like operator. 
V. A. Fateev (Laboratoire de Physique Mathematique, Universite' de   Montpellier II, Montpellier, France), R. De Pietri (Dip...