From Trojan Dust Clouds to Nonneutral Plasmas: A Universality Class of Metastable Hamiltonian Systems

We propose that long-lived confined nonneutral plasmas belong to a broader universality class of dynamical systems characterized by Hamiltonian core dynamics, strong constraints, weak dissipation, and metastability protected by spectral gaps. Motivated by recent work on Trojan dust clouds near the L4 and L5 equilibria of the restricted three-body problem, we introduce the Trojan Universality Class (TUC) and demonstrate that nonneutral plasmas confined in Penning-Malmberg traps constitute a second canonical realization of this class. In both systems, confinement persists on timescales vastly exceeding natural dynamical periods and fails abruptly only after slow, resonance-mediated transport erodes adiabatic invariants. By reframing nonneutral plasma confinement in the language of spectral gaps, resonance overlap, and Nekhoroshev-type timescales, the TUC provides a unified conceptual framework that explains observed longevity, halo formation, and sudden confinement loss. This perspective yields new diagnostics, predictive criteria for confinement failure, and experimentally testable signatures that go beyond traditional stability or transport analyses.