“…The Hamiltonian (1.1) may appear not-too-familiar to many readers, but, as a matter of fact, the corresponding classical Hamiltonian system frequently arises as a controlled approximation to weakly nonlinear partial differential equations (PDEs) in strongly resonant domains, originating from a number of branches of physics and mathematics. Specifically, classical systems corresponding to (1.1), together with some closely related variations, have been studied in the following contexts: gravitational dynamics in anti-de Sitter (AdS) spacetimes [40][41][42][43][44][45][46] (typically, motivated by the AdS instability conjecture [47,48]); related dynamical problems for classical relativistic fields [49][50][51][52][53][54]; nonrelativistic nonlinear Schrödinger equations describing, among other things, the dynamics of Bose-Einstein condensates in harmonic potentials [55][56][57][58][59][60][61][62][63]; and integrable models for turbulence [64][65][66]. These classical systems display, for different choices of C nmkl , a wide range of analytic and dynamical patterns ranging from full solvability [64] to Lax-integrability [64][65][66], partial solvability [49][50][51][52]58,59,67], turbulent cascades [42,…”