Quantizing the classical cat

摘要

A mathematical analysis of a pendulum system reveals the relevance to quantum systems of the classical concept of 'monodromy' -- why a falling cat always lands the right way up. A central problem in modern physics is to find effective methods for quantizing classical dynamical systems -- modifying the classical equations to incorporate the effects of quantum mechanics. One of the main obstacles is the disparity between the linearity of quantum theory and the nonlinearity of classical dynamics. Takinga big step forward, R. H. Cushman et al. have analysed a quantum version of the spring pendulum, whose resonant state was first discussed by Enrico Fermi and which is a standard model for the carbon dioxide molecule.