The fluid equations for the baryon-electron system in an expanding universe are derived from the Boltzmann equation. The effect of the Compton interaction is taken into account properly in order to evaluate the photon-electron collisional term. As an application, the acoustic motions of the baryon-electron system after recombination are investigated. The effective adiabatic index [Formula presented] is computed for sound waves of various wavelengths, assuming the perturbation amplitude is small. The oscillations are found to be dumped when [Formula presented] changes from between 1 (for an isothermal process) to 5/3 (for an adiabatic process).
|Number of pages||12|
|Journal||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|Publication status||Published - 1997|
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- Physics and Astronomy (miscellaneous)