  Polarized models of relativistically hot astrophysical plasmas require
transport coefficients as input: synchrotron absorption and emission
coefficients in each of the four Stokes parameters, as well as three Faraday
rotation coefficients. Approximations are known for all coefficients for a
small set of electron distribution functions, such as the Maxwell-Juttner
relativistic thermal distribution, and a general procedure has been obtained by
Huang & Shcherbakov for an isotropic distribution function. Here we provide an
alternative general procedure, with a full derivation, for calculating
absorption and rotation coefficients for an arbitrary isotropic distribution
function. Our method involves the computation of the full plasma susceptibility
tensor, which in addition to absorption and rotation coefficients may be used
to determine plasma modes and the dispersion relation. We implement the scheme
in a publicly available library with a simple interface, thus allowing for easy
incorporation into radiation transport codes. We also provide a comprehensive
survey of the literature and comparison with earlier results.
