Polarization Observations of the Microwave Background Radiation with the Cosmic Background Imager

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AST-0206416Readhead, AnthonyThe cosmic microwave background radiation (CMBR) is expected to be polarized at a level of about 10%, owing to Thomson scattering, but as yet this polarization has not been detected. The Cosmic Background Interferometer (CBI) has been measuring the total intensity of the CMBR for the past two years, and with minor modifications to the receivers and the observing strategy, the CBI should be able to detect the polarization within a year. It should also measure the angular power spectrum of polarized fluctuations, if the predictions of currently favored cosmological models arecorrect. Polarization observations of the microwave background radiation will provide a number of important tests of cosmological models. For example many cosmological models with non-standard primordial power spectra are degenerate with standard models having different values of key cosmological parameters. It is possible to further test the predictions of the models and to break these degeneracies by measuring the polarization power spectrum and the cross-correlation between polarization and total intensity. Polarization observations should also help to reduce the uncertainties in key cosmological parameters, such as the baryon density, the matter density and the cosmological constant, and to place stringent limits on the epoch of reionization. This award will allow use of the CBI to make high sensitivity (1 MK) polarization observations of the cosmic microwave background radiation over the angular multipole range l = 300-1700.***