  In this paper we discuss the dynamics of charged particles in high-intensity
laser fields in the context of the Frenet-Serret formalism, which describes the
intrinsic geometry of particle worldlines. We find approximate relations for
the Frenet-Serret scalars and basis vectors relevant for high-intensity laser
particle interactions. The onset of quantum effects relates to the curvature
radius of classical trajectories being on the order of the Compton wavelength.
The effects of classical radiation reaction are discussed, as well as the
classical precession of the spin-polarization vector according to the
Thomas-Bargman-Michel-Telegdi (T-BMT) equation. We comment on the derivation of
the photon emission rate in strong-field QED beyond the locally constant field
approximation, which is used in Monte Carlo simulations of quantum radiation
reaction. Such a numerical simulation is presented for a possible experiment to
distinguish between classical and quantum mechanical models of radiation
reaction.
