Quantum resonant systems, integrable and chaotic

Oleg Evnin, Worapat Piensuk

Research output: Contribution to journalArticle

4 Citations (Scopus)


Resonant systems emerge as weakly nonlinear approximations to problems with highly resonant linearized perturbations. Examples include nonlinear Schrödinger equations in harmonic potentials and nonlinear dynamics in anti-de Sitter spacetime. The classical dynamics within this class of systems can be very rich, ranging from fully integrable to chaotic as one changes the values of the mode coupling coefficients. Here, we initiate a study of quantum infinite-dimensional resonant systems, which are mathematically a highly special case of two-body interaction Hamiltonians (extensively researched in condensed matter, nuclear and high-energy physics). Despite the complexity of the corresponding classical dynamics, the quantum version turns out to be remarkably simple: the Hamiltonian is block-diagonal in the Fock basis, with all blocks of varying finite sizes. Being solvable in terms of diagonalizing finite numerical matrices, these systems are thus arguably the simplest interacting quantum field theories known to man. We demonstrate how to perform the diagonalization in practice, and study both numerical patterns emerging for the integrable cases, and the spectral statistics, which efficiently distinguishes the special integrable cases from generic (chaotic) points in the parameter space. We discuss a range of potential applications in view of the computational simplicity and dynamical richness of quantum resonant systems.

Original languageEnglish
Article number025102
Number of pages20
JournalJournal of Physics. A, Mathematical and Theoretical
Issue number2
Publication statusPublished - 13 Dec 2018

Bibliographical note

v2: slightly expanded published version


  • integrability
  • quantum chaos
  • quantum field theory
  • random matrix theory
  • spectral statistics
  • turbulence

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