Circular Polarization Of Cosmic Microwave Background Research Articles

Characterization of a half-wave plate for cosmic microwave background circular polarization measurement with POLARBEAR.

A half-wave plate (HWP) is often used as a modulator to suppress systematic error in the measurements of cosmic microwave background (CMB) polarization. A HWP can also be used to measure circular polarization (CP) through its optical leakage from CP to linear polarization. The CP of the CMB is predicted from various sources, such as interactions in the Universe and extension of the standard model. Interaction with supernova remnants of population III stars is one of the brightest CP sources. Thus, the observation of the CP of CMB is a new tool for searching for population III stars. In this paper, we demonstrate the improved measurement of the leakage coefficient using the transmission measurement of an actual HWP in the laboratory. We measured the transmittance of linearly polarized light through the HWP used in Polarbear in the frequency range of 120-160GHz. We evaluate the properties of the HWP by fitting the data with a physical model using the Markov Chain Monte Carlo method. We then estimate the band-averaged CP leakage coefficient using the physical model. We find that the leakage coefficient strongly depends on the spectra of CP sources. We thus calculate the maximum fractional leakage coefficient from CP to linear polarization as 0.133 ± 0.009 in the Rayleigh-Jeans spectrum. The nonzero value shows that Polarbear has a sensitivity to CP. Additionally, because we use the bandpass of detectors installed in the telescope to calculate the band-averaged values, we also consider systematic effects in the experiment.

CMB circular and B -mode polarization from new interactions

Standard models describing the radiation transfer of the cosmic microwave background (CMB) through Compton scattering predict that cosmological scalar perturbations at linear order are not able to source V and B polarization modes. In this work, we investigate the possibility that such CMB polarization modes are generated even in the presence of linear scalar perturbations only. We provide a general parametrization of the photon-fermion forward-scattering amplitude and compute mixing terms between different CMB polarization modes. We discuss different general extensions of Standard Model interactions which violate discrete symmetries, while preserving the combination of charge conjugation, parity and time reversal. We show that it is possible to source CMB circular polarization by violating parity and charge conjugation symmetries. Instead, B-mode generation is associated to the violation of symmetry for time-reversal. Our results provide a useful tool to constrain new physics using CMB data.

On the CMB circular polarization: I. The Cotton\u2013Mouton effect

Generation of cosmic microwave background (CMB) elliptic polarization due to the Cotton–Mouton (CM) effect in a cosmic magnetic field is studied. We concentrate on the generation of CMB circular polarization and on the rotation angle of the CMB polarization plane from the decoupling time until at present. For the first time, a rather detailed analysis of the CM effect for an arbitrary direction of the cosmic magnetic field with respect to photon direction of propagation is done. Considering the CMB linearly polarized at the decoupling time, it is shown that the CM effect is one of the most substantial effects in generating circular polarization especially in the low part of the CMB spectrum. It is shown that in the frequency range 10^8 Hz le nu _0le 10^9 Hz, the degree of circular polarization of the CMB at present for perpendicular propagation with respect to the cosmic magnetic field is in the range 10^{-13}lesssim P_C(t_0)lesssim 7.65times 10^{-7} or Stokes circular polarization parameter 2.7 times 10^{-13} K lesssim |V(t_0)|lesssim 2 times 10^{-6} K for values of the cosmic magnetic field amplitude at present in the range 10^{-9} G lesssim Blesssim 8times 10^{-8} G. On the other hand, for not perpendicular propagation with respect to the cosmic magnetic field we find 10^{-15}lesssim P_C(t_0)lesssim 6times 10^{-12} or 2.72 times 10^{-15} K lesssim |V(t_0)| lesssim 10^{-11} K, for the same values of the cosmic magnetic field amplitude and same frequency range. Estimates on the rotation angle of the CMB polarization plane delta psi _0 due to the CM effect and constraints on the cosmic magnetic field amplitude from current constraints on delta psi _0 due to a combination of the CM and Faraday effects are found.

Generation of circular polarization of CMB via polarized Compton scattering

The standard scenario of cosmology which includes only Compton scattering predicts a measurable amount for the linear polarization of the cosmic microwave background (CMB) radiation, while trough this scenario there is no any sources to generate circular polarization. The circular polarization of CMB has not been observed so far, however it has not been completely excluded from observational evidences, for example, SPIDER group constraints on l(l+1)CVl/(2π) for 33<l<307 in the range of 141 μ K2 to 255 μ K2 at 150 GHz, providing 95% C.L. On the other hand, over the last few years, many theoretical works have been done to investigate the generation of CMB circular polarization. In this paper, it is revealed that Compton scattering of CMB photons from polarized cosmic electrons with none-zero bulk velocity ve≠0 (polarized Compton scattering) can generate circular polarization. The effects of the external magnetic field on large scale, chiral magnetic instability and new physics interactions on the distribution of cosmic electrons can be considered as possible sources of the polarized cosmic electrons. We show that the power spectrum of circular polarization of CMB ClV(S) generated by polarized Compton scattering in the presence of scalar perturbation is proportional to the power spectrum of temperature fluctuation ClI(S) and δ2 where δ is the fraction of polarized electron number density to the total one. Also it has been discussed that δ<10−4 is required to find consistency with the reported upper limit of CMB circular polarization.

A New Limit on CMB Circular Polarization from SPIDER

Abstract We present a new upper limit on cosmic microwave background (CMB) circular polarization from the 2015 flight of Spider, a balloon-borne telescope designed to search for B-mode linear polarization from cosmic inflation. Although the level of circular polarization in the CMB is predicted to be very small, experimental limits provide a valuable test of the underlying models. By exploiting the nonzero circular-to-linear polarization coupling of the half-wave plate polarization modulators, data from Spider's 2015 Antarctic flight provide a constraint on Stokes V at 95 and 150 GHz in the range 33 &lt; ℓ &lt; 307 . No other limits exist over this full range of angular scales, and Spider improves on the previous limit by several orders of magnitude, providing 95% C.L. constraints on ℓ ( ℓ + 1 ) C ℓ VV / ( 2 π ) ranging from 141 to 255 μK2 at 150 GHz for a thermal CMB spectrum. As linear CMB polarization experiments become increasingly sensitive, the techniques described in this paper can be applied to obtain even stronger constraints on circular polarization.

Photon-photon interactions as a source of cosmic microwave background circular polarization

Photon-photon interactions, as described with the standard Heisenberg-Euler interaction, can transform plane polarization of the CMB into circular polarization, in the period right after last scattering. We estimate the distribution of the resulting circular polarization parameters, as constrained by confining observations to very small angular regions of large plane polarization, and find results of the order of 1 0 - 9 for the Stokes parameter V in some of these regions.

An improved upper limit to the CMB circular polarization at large angular scales

Circular polarization of the Cosmic Microwave Background (CMB) offers thepossibility of detecting rotations of the universe and magneticfields in the primeval universe or in distant clusters of galaxies. We used the MilanoPolarimeter (MIPOL) installed at the Testa Grigia Observatory, on the italian Alps,to improve the existing upper limits to the CMBcircular polarization at large angular scales. We obtain 95% confidence level upper limits to the degree of the CMB circular polarization rangingbetween 5.0⋅10−4 and 0.7⋅10−4at angular scales between 8° and 24°, improvingby one order of magnitude preexisting upper limits at large angular scales.Our results are still far from thenK region where today expectations place the amplitude of the V Stokesparameter used to characterize circular polarization of the CMB but improvethe preexisting limit at similar angular scales.Our observations offered also the opportunity of characterizingthe atmospheric emission at 33 GHz at the Testa Grigia Observatory.

Signatures of pseudoscalar photon mixing in CMB polarization

We study the effect of photon and ultralight pseudoscalar mixing on the propagation of electromagnetic radiation through the extragalactic medium. The medium is modeled as a large number of uncorrelated magnetic domains. We obtain an analytic expression for the different Stokes parameters in the limit of a small mixing angle. Stokes parameters are found to change linearly with the number of domains. We verify this result by direct numerical simulations. We use the formalism to estimate the effect of pseudoscalar-photon mixing on the cosmic microwave background (CMB) polarization. We impose limits on the model parameters consistent with CMB observations. We find that the currently allowed parameter range admits a CMB circular polarization up to order ${10}^{\ensuremath{-}7}$.