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We compute the imprints left on the CMB by two cosmic reionization models consistent with current observations but characterized by alternative radiative feedback prescriptions (suppression and filtering) resulting in a different suppression of star formation in low-mass halos. The models imply different ionization and thermal histories and 21 cm background signals. The derived Comptonization, u, and free-free distortion, y_B, parameters are below current observational limits for both models. However, the value of u = 1.69 * 10^-7 (9.65 * 10^-8) for the suppression (filtering) model is in the detectability range of the next generation of CMB spectrum experiments. Through the dedicated Boltzmann code CMBFAST, modified to include the above ionization histories, we compute the CMB angular power spectrum (APS) of the TT, TE, and EE modes. For the EE mode the differences between these models are significantly larger than the cosmic and sampling variance over the multipole range l = 5-15, leaving a good chance of discriminating between these feedback mechanisms with forthcoming/future CMB polarization experiments. The main limitations come from foreground contamination: it should be subtracted at per cent level in terms of APS, a result potentially achievable by novel component separation techniques and mapping of Galactic foreground.
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We show that a non-minimal coupling of electromagnetism with background torsion can produce birefringence of the electromagnetic waves. This birefringence gives rise to a B-mode polarization of the CMB. From the bounds on B-mode from WMAP and BOOMERanG data, one can put limits on the background torsion at $xi_{1}T_{1}=(-3.35 pm 2.65) times 10^{-22} GeV^{-1}$.
Cosmic microwave background polarization encodes information not only on the early universe but also dark energy, neutrino mass, and gravity in the late universe through CMB lensing. Ground based surveys such as ACTpol, PolarBear, SPTpol significantly complement cosmological constraints from the Planck satellite, strengthening the CMB dark energy figure of merit and neutrino mass constraints by factors of 3-4. This changes the dark energy probe landscape. We evaluate the state of knowledge in 2017 from ongoing experiments including dark energy surveys (supernovae, weak lensing, galaxy clustering), fitting for dynamical dark energy, neutrino mass, and a modified gravitational growth index. Adding a modest strong lensing time delay survey improves those dark energy constraints by a further 32%, and an enhanced low redshift supernova program improves them by 26%.
We investigate the primordial phase of the Universe in the context of brane inflation modeled by Bogomolnyi-Prasad-Sommerfield (BPS) domain walls solutions of a bosonic sector of a 5D supergravity inspired theory. The solutions are embedded into five dimensions and it is assumed that they interact with each other due to elastic particle collisions in the bulk. A four-dimensional arctan-type inflaton potential drives the accelerated expansion phase and predicts observational quantities in good agreement with the currently available Cosmic Microwave Background data.
We constrain parity-violating interactions to the surface of last scattering using spectra from the QUaD experiments second and third seasons of observations by searching for a possible systematic rotation of the polarization directions of CMB photons. We measure the rotation angle due to such a possible cosmological birefringence to be 0.55 deg. +/- 0.82 deg. (random) +/- 0.5 deg. (systematic) using QUaDs 100 and 150 GHz TB and EB spectra over the multipole range 200 < l < 2000, consistent with null, and constrain Lorentz violating interactions to < 2^-43 GeV (68% confidence limit). This is the best constraint to date on electrodynamic parity violation on cosmological scales.
Most cosmic microwave background experiments observe the sky along circular or near-circular scans on the celestial sphere. For such experiments, we show that simple linear systems connect the Fourier spectra of temperature and polarization time-ordered data to the harmonic spectra of T, E and B on the sphere. We show how this can be used to estimate those spectra directly from data streams. In addition, the inversion of the linear system that connects Fourier spectra to angular power spectra offers a natural way to down-weight those modes of observation most contaminated by low-frequency noise, ground pickup, or fluctuations of atmospheric emission on large angular scale. This can be of interest for the analysis of future CMB data sets, as an alternative or in complement to other approaches that involve map-making as a first analysis step.
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