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The energy‐level sequence, whose spacings distribution is the most frequently invoked indicator of quantum chaos, can be derived (for systems with two degrees of freedom) from a two‐dimensional representation of quantum invariants by projection. In this representation, such properties of level sequences as effective randomness in integrable models and level repulsion in nonintegrable models can be more directly interpreted in terms of physical properties. In integrable models, anharmonicities convert quasiperiodic level sequences into effectively random sequences.

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Copyright 1990 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

The following article appeared in Journal of Applied Physics and may be found at