Reionization and the Cosmic Microwave Background

If the COBE detection of CMB fluctuations is used to normalize the power spectrum of primordial density fluctuations in a cold dark matter–dominated universe, early reionization is likely to result in a substantial diminution of primordial temperature fluctuations on degree scales. I argue that the reionization may be non–Gaussian because of feedback effects. Secondary fluctuations on arc–minute scales provide an important probe of the efficiency of rescattering.