  We consider multi-class systems of interacting nonlinear Hawkes processes
modeling several large families of neurons and study their mean field limits.
As the total number of neurons goes to infinity we prove that the evolution
within each class can be described by a nonlinear limit differential equation
driven by a Poisson random measure, and state associated central limit
theorems. We study situations in which the limit system exhibits oscillatory
behavior, and relate the results to certain piecewise deterministic Markov
processes and their diffusion approximations.

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