  Demonstrating how microscopic dynamics cause large systems to approach
thermal equilibrium remains an elusive, longstanding, and actively-pursued goal
of statistical mechanics. We identify here a dynamical mechanism for
thermalization in a general class of two-component dynamical Lorentz gases, and
prove that each component, even when maintained in a non-equilibrium state
itself, can drive the other to a thermal state with a well-defined effective
temperature.
