Quantum chaos viewed from quantum action
  We consider a mixed chaotic Hamiltonian system and compare classical with quantum chaos. As alternative to the methods of enegy level spacing statistics and trace formulas, we construct a quantum action and a quantum analogue phase space to analyse quantum chaos. 
D. Huard, H. Kr\"oger, G. Melkonyan, L.P. Nadeau, K.J.M. Moriarty