Polarization Power Spectra Research Articles

Polarization of the microwave background in reionized models

I discuss the physics of polarization in models with early reionization. For sufficiently high optical depth to recombination the polarization is boosted on large scales while it is suppressed on smaller scales. New peaks appear in the polarization power spectrum, their position is proportional to the square root of the redshift at which the reionization occurs while their amplitude is proportional to the optical depth. For standard scenarios the rms degree of linear polarization as measured with a 7 degree FWHM antenna (like the one of the Brown University experiment) is $1.6\mu K$, $1.2 \mu K$, $4.8\times 10^{-2} \mu K$ for an optical depth of 1, 0.5 or 0 respectively. For a 1 degree FWHM antenna this same models give $2.7 \mu K$ , $1.8 \mu K$ and $0.77 \mu K$. Detailed measurement of polarization on large angular scales could provide an accurate determination of the epoch of reionization, which cannot be obtained from temperature measurements alone.

Stokes Parameters in Cosmic Microwave Background Measurements

We compute numerically the scalar- and tensor-mode induced Stokes parameters of the cosmic microwave background, by taking into account the basis rotation effects. It is found that the tensor contribution to the polarization power spectrum get enhanced and dominates over the scalar contribution for low multipoles in a universe with or without recombination. Furthermore, we show that all full-sky averaged two-point cross-correlation functions of the Stokes parameters vanish. We thus comment on the cross-correlation between the anisotropy and polarization of the CMB, and calculate the expected signal to noise ratio for the polarization experiment underway.

Digital Computer Simulation for Prediction and Analysis of Electromagnetic Interference

A digital computer simulation program is described for use by communications systems and equipment designers who must consider electromagnetic interference. The program determines the interference experienced by a test receiver in a signal environment resulting from its associated transmitter, a large deployment of potentially interfering transmitters, and by atmospheric and cosmic noise sources. Simulation models are designed to represent such transmitter characteristics as antenna gain and scan patterns, polarization and emitted power spectrum; other models represent propagation phenomena such as scattering, reflection, fading and tropospheric refraction; and such receiver characteristics as antenna gain patterns, frequency selectivity and demodulator transfer characteristics. Signal acceptability criteria are included to permit system scoring. Program flexibility is stressed so that optimum system design may be achieved through rapid evaluation of successive approximations.