Non-Concentration of Quasimodes for Integrable Systems

Jared Wunsch*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


We consider the possible concentration in phase space of a sequence of eigenfunctions (or, more generally, a quasimode) of an operator whose principal symbol has completely integrable Hamilton flow. The semiclassical wavefront set WF h of such a sequence is invariant under the Hamilton flow. In principle this may allow concentration of WF h along a single closed orbit if all frequencies of the flow are rationally related. We show that, subject to non-degeneracy hypotheses, this concentration may not in fact occur. Indeed, in the two-dimensional case, we show that WF h must fill out an entire Lagrangian torus. The main tools are the spreading of Lagrangian regularity previously shown by the author, and an analysis of higher order transport equations satisfied by the principal symbol of a Lagrangian quasimode. These yield a unique continuation theorem for the principal symbol of Lagrangian quasimode, which is the principal new result of the paper.

Original languageEnglish (US)
Pages (from-to)1430-1444
Number of pages15
JournalCommunications in Partial Differential Equations
Issue number8
StatePublished - Aug 2012


  • Eigenfunction
  • Lagrangian
  • Quasimode
  • Semiclassical
  • Wavefront

ASJC Scopus subject areas

  • Analysis
  • Applied Mathematics


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