Partially polarized black-body radiation

Roman Tomaschitz

Physica A: Statistical Mechanics and its Applications, 2019, vol. 524, issue C, 130-146

Abstract: Angular temperature fluctuations in a photon gas generate fractional polarization of the black-body spectrum. The spectral density consists of two Planckians with different temperature variables representing orthogonal polarization states. The angular-dependent fluctuating temperature variables can be inferred from the Stokes parameters which have been measured, over the full solid angle, for the cosmic microwave background (CMB) radiation. The polarization matrix of a partially polarized photon gas is obtained by way of a unitary transformation of the annihilation and creation operators. The radiation is decomposed into a totally polarized and an unpolarized intensity component, and the polarization fraction is calculated, which is very small, of order ∼10−7, for the nearly isotropic CMB radiation. Spatial energy density autocorrelations induced by polarization and temperature anisotropy are derived and isotropized by an angular average. These correlations are long-range, exhibiting power-law decay ∝1∕r6 at large distance, and much stronger than the energy density correlation of an ideal photon gas which decays ∝1∕r8. As for the CMB radiation, the spatial energy density correlations are calculated from analytic Gaussian fits to the measured temperature and polarization power spectra, including the crossover from the short-distance regime to the asymptotic power-law decay.

Keywords: Polarized photon gas; Polarization fraction; Stokes parameters of anisotropic black-body radiation; Multipole expansion of angular fluctuations; Spatial energy density correlations; Cosmic microwave background radiation (search for similar items in EconPapers)
Date: 2019
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:phsmap:v:524:y:2019:i:c:p:130-146

DOI: 10.1016/j.physa.2019.03.014

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