Resummed Kinetic Field Theory: a model of coupled baryonic and dark
  matter
  We present a new analytical description of cosmic structure formation in a
mixture of dark and baryonic matter, using the framework of Kinetic Field
Theory (KFT) -- a statistical field theory for classical particle dynamics. So
far, KFT has only been able to describe a single type of particles, sufficient
to consider structure growth due to the gravitational interactions between dark
matter. However, the influence of baryonic gas dynamics becomes increasingly
relevant when describing smaller scales. In this paper, we thus demonstrate how
to extend the KFT formalism as well as a previously presented resummation
scheme towards describing such mixtures of two particle species. Thereby, the
gas dynamics of baryons are accounted for using the recently developed model of
Mesoscopic Particle Hydrodynamics. Assuming a flat $\Lambda$CDM Universe and a
simplified model for the thermal gas evolution, we demonstrate the validity of
this approach by computing the linear evolution of the individual and total
matter power spectra between the epoch of recombination and today. Our results
correctly reproduce the expected behaviour, showing a suppression of both
baryonic and dark matter structure growth on scales smaller than the baryonic
Jeans length, in good agreement with results from the numerical Boltzmann
solver CLASS. Nonlinear corrections within this approach will be investigated
in upcoming works.
