What does quantum chaos mean?
  We discuss how the concept of the quantum action can be used to characterize quantum chaos. As an example we study quantum mechanics of the inverse square potential in order to test some questions related to quantum action. Quantum chaos is discussed for the 2-D hamiltonian system of harmonic oscillators with anharmonic coupling. 
D. Huard, H. Kroger, G.G. Melkonyan, K.J.M. Moriarty and L.P. Nadeau