  We explore a minimal paradigm for thermalization, consisting of two
weakly-coupled, low dimensional, non-integrable subsystems. As demonstrated for
Bose-Hubbard trimers, chaotic ergodicity results in a diffusive response of
each subsystem, insensitive to the details of the drive exerted on it by the
other. This supports the hypothesis that thermalization can be described by a
Fokker Plank equation. We also observe, however, that Levy-flight type
anomalies may arise in mesoscopic systems, due to the wide range of time scales
that characterize `sticky' dynamics.
