We study partially coherent fields that have a coherent-mode representation in the orbital-angular-momentummode basis. For such fields, we introduce the concepts of the angular coherence function and the coherence angle. Such fields are naturally produced by the process of parametric down-conversion—a second-order nonlinear optical process in which a pump photon breaks up into two entangled pho...

A critical examination is made of the somewhat loose and incomplete statement that a polar diagram is the Fourier transform of an aperture distribution. By aperture distribution it is necessary to understand, in the two-dimensional case, distribution across the aperture of the component along the aperture plane of the electromagnetic field in the plane of propagation. Furthermore, the concept o...

We discuss cosmic microwave background anisotropies in models with an unconventional primordial power spectrum. In particular, we consider an initial power spectrum with some “spiky” corrections. Interestingly, such a primordial power spectrum generates “wavy” structure in the CMB angular power spectrum. Some possible models generating such a primordial power spectrum from inflaton dynamics are...

The two point angular correlation function is an excellent measure of structure in the universe. To extract from it the three dimensional power spectrum, one must invert Limber’s Equation. Here we perform this inversion using a Bayesian prior constraining the smoothness of the power spectrum. Among other virtues, this technique allows for the possibility that the estimates of the angular correl...

We report on the first flight of the balloon-borne QMAP experiment. The experiment is designed to make a map of the cosmic microwave background anisotropy on angular scales from 0. ◦70 to several degrees. Using the map we determine the angular power spectrum of the anisotropy in multipole bands from l ∼ 40 to l ∼ 140. The results are consistent with the Saskatoon (SK) measurements. The frequenc...

We study the effect of a finite topology on the temperature correlations of the cosmic microwave background in a flat universe. Analytic expressions for the angular power spectrum are given for all possible finite flat models. We examine the angular correlation function itself, pointing out visible and discrete features that arise from topology. While observations of the power spectrum on large...

Statistical characteristics of the angular power spectrum of scattered radiation for power law spectrum of electron density fluctuations in turbulent collisional anisotropic magnetized plasma are considered.