  We explore how interactions between baryons and photons can be incorporated
into Kinetic Field Theory (KFT), a description of cosmic structure formation
based on classical Hamiltonian particle dynamics. In KFT, baryons are described
as effective mesoscopic particles which represent fluid elements governed by
the hydrodynamic equations. In this paper, we modify the mesoscopic particle
model to include pressure effects exerted on baryonic matter through
interactions with photons. As a proof of concept, we use this extended
mesoscopic model to describe the tightly coupled baryon-photon fluid between
matter-radiation equality and recombination. We show that this model can
qualitatively reproduce the formation of baryon-acoustic oscillations in the
cosmological power spectrum.
