Quantum Surface of Section Method: Eigenstates and Unitary Quantum Poincaré Evolution

The unitary representation of exact quantum Poincaré mapping is constructed. It is equivalent to the compact representation [19, 22, 23] in a sense that it yields equivalent quantization condition with important advantage over the compact version: since it preserves the probability it can be literally interpreted as the quantum Poincaré mapping which generates quantum time evolution at fixed energy between two successive crossings with surface of section (SOS). SOS coherent state representation (SOS Husimi distribution) of arbitrary (either stationary or evolving) quantum SOS state (vector from the Hilbert space over the configurational SOS) is introduced. Dynamical properties of SOS states can be quantitatively studied in terms of the so called localization areas which are defined through information entropies of their SOS coherent state representations. In the second part of the paper I report on results of extensive numerical application of quantum SOS method in a generic but simple 2-dim Hamiltonian system, namely semiseparable oscillator. I have calculated the stretch of 13 500 consecutive eigenstates with the largest sequential quantum number around 18 million and obtained the following results: (i) the validity of the semiclassical Berry-Robnik formula for level spacing statistics was confirmed and using the concept of localization area the states were quantitatively classified as regular or chaotic, (ii) the classical and quantum Poincaré evolution were performed and compared, and expected agreement was found, (iii) I studied few examples of wavefunctions and particularly, SOS coherent state representation of regular and chaotic eigenstates and analyzed statistical properties of their zeros which were shown on the chaotic component of 2-dim SOS to be uniformly distributed with the cubic repulsion between nearest neighbours.