Small-scale cosmic microwave background anisotropies as probe of the geometry of the universe

We perform detailed calculations of cosmic microwave background (CMB) anisotropies in a CDM-dominated open universe with primordial adiabatic density perturbations for a variety of reionization histories. The CMB anisotropies depend primarily on the geometry of the universe, which in a matter-dominated universe is determined by OMEGA, and the optical depth to the surface of last scattering. In particular, the location of the primary Doppler peak depends primarily on R and is fairly insensitive to the other unknown parameters, such as OMEGAb_, h, DELTA, and the shape of the power spectrum. Therefore, if the primordial density perturbations are adiabatic, measurements of CMB anisotropies on small scales may be used to determine OMEGA. Subject Headings: cosmic microwave background - cosmology: theory - intergalactic medium - large-scale structure of universe