In recent years the goal of estimating different cosmological parameters precisely has set new challenges in the effort to accurately measure the angular power spectrum of CMB. This has required removal of foreground contamination as well as detector noise bias with reliability and precision. Recently, a novel {\em model-independent} method for the estimation of CMB angular power spectrum solely from multi-frequency observations has been proposed and implemented on the first year WMAP data by Saha et al. 2006. All previous estimates of power spectrum of CMB are based upon foreground templates using data sets from different experiments. However our methodology demonstrates that {\em CMB angular spectrum can be reliably estimated with precision from a self contained analysis of the WMAP data}. In this work we provide a detailed description of this method. We also study and identify the biases present in our power spectrum estimate. We apply our methodoly to extract the power spectrum from the WMAP 1 year and 3 year data.Comment: 38 pages, 17 figure

We introduce new symmetry-based methods to test for isotropy in cosmic microwave background (CMB) radiation. Each angular multipole is factored into unique products of power eigenvectors, related multipoles and singular values that provide two new rotationally invariant measures mode by mode. The power entropy and directional entropy are new tests of randomness that are independent of the usual CMB power. Simulated Galactic plane contamination is readily identified. The ILC-WMAP data maps show seven axes well aligned with one another and the direction Virgo. Parameter free statistics find 12 independent cases of extraordinary axial alignment, low power entropy, or both having 5 per cent probability or lower in an isotropic distribution. Isotropy of the ILC maps is ruled out to confidence levels of better than 99.9 per cent, whether or not coincidences with other puzzles coming from the Virgo axis are included. Our work shows that anisotropy is not confined to the low l region, but extends over a much larger l range.

Accurate measurements of angular power spectrum of Cosmic Microwave Background (CMB) radiation has lead to marked improvement in the estimates of different cosmological parameters. This has required removal of foreground contamination as well as detector noise bias with reliability and precision. We present the estimation of CMB angular power spectrum from the multi-frequency observations of WMAP using a novel model-independent method. The primary product of WMAP are the observations of CMB in 10 independent difference assemblies (DA) that have uncorrelated noise. Our method utilizes maximum information available within WMAP data by linearly combining all the DA maps to remove foregrounds and estimating the power spectrum from cross power spectra of clean maps with independent noise. We compute 24 cross power spectra which are the basis of the final power spectrum. The binned average power matches with WMAP team's published power spectrum closely. A small systematic difference at large multipoles is accounted for by the correction for the expected residual power from unresolved point sources. The correction is small and significantly tempered. Previous estimates have depended on foreground templates built using extraneous observational input. This is the first demonstration that the CMB angular spectrum can be reliably estimated with precision from a self contained analysis of the WMAP data.

We analyze the 3 yr Wilkinson Microwave Anisotropy Probe (WMAP) temperature anisotropy data seeking to confirm the power spectrum and likelihoods published by the WMAP team. We apply five independent implementations of four algorithms to the power spectrum estimation and two implementations to the parameter estimation. Our single most important result is that we broadly confirm the WMAP power spectrum and analysis. Still, we do find two small but potentially important discrepancies. On large angular scales there is a small power excess in the WMAP spectrum (5%Y10% at ' P 30) primarily due to likelihood approximation issues between 13 ' P30. On small angular scales there is a systematic difference between the V-and W-band spectra (few percent at ' k300). Recently, the latter discrepancy was explained by Huffenberger et al. (2006) in terms of oversubtraction of unresolved point sources. As far as the low-' bias is concerned, most parameters are affected by a few tenths of a . The most important effect is seen in n s . For the combination of WMAP, ACBAR, and BOOMERANG, the significance of n s 6 ¼ 1 drops from $2.7 to $2.3 when correcting for this bias. We propose a few simple improvements to the low-' WMAP likelihood code, and introduce two important extensions to the Gibbs sampling method that allows for proper sampling of the low signal-to-noise ratio regime. Finally, we make the products from the Gibbs sampling analysis publicly available, thereby providing a fast and simple route to the exact likelihood without the need of expensive matrix inversions. Subject headingg s: cosmic microwave background -cosmology: observations -methods: numerical

Radiation propagating over cosmological distances can probe light weakly interacting pseudoscalar (or scalar) particles. The existence of a spin-0 field changes the dynamical symmetries of electrodynamics. It predicts spontaneous generation of polarization of electromagnetic waves due to mode mixing in the presence of background magnetic field. We illustrate this by calculations of propagation in a uniform medium, as well as in a slowly varying background medium, and finally with resonant mixing. Highly complicated correlations between different Stokes parameters are predicted depending on the parameter regimes. The polarization of propagating waves shows interesting and complex dependence on frequency, the distance of propagation, coupling constants, and parameters of the background medium such as the plasma density and the magnetic field strength. For the first time we study the resonant mixing of electromagnetic waves with the scalar field, which occurs when the background plasma frequency becomes equal to the mass of the scalar field at some point along the path. Dynamical effects are found to be considerably enhanced in this case. We also formulate the condition under which the adiabatic approximation can be used consistently, and find caveats about comparing different frequency regimes.

No abstract

Recently, a symmetry-based method to test for statistical isotropy of the cosmic microwave background was developed. We apply the method to template-cleaned 3-and 5-years Wilkinson Microwave Anisotropy Probe-Differencing Assembly maps. We examine a wide range of angular multipoles from 2 < l < 300. The analysis detects statistically significant signals of anisotropy inconsistent with an isotropic cosmic microwave background in some of the foreground-cleaned maps. We are unable to resolve whether the anomalies have a cosmological, local astrophysical or instrumental origin. Assuming the anisotropy arises due to residual foreground contamination, we estimate the residual foreground power in the maps. For the W-band maps, we also find a highly improbable degree of isotropy we cannot explain. We speculate that excess isotropy may be caused by faulty modelling of detector noise.

We solve the general problem of mixing of electromagnetic and scalar or pseudoscalar fields coupled by axion-type interactions L int = g φ φ ǫ µναβ F µν F αβ . The problem depends on several dimensionful scales, including the magnitude and direction of background magnetic field, the pseudoscalar mass, plasma frequency, propagation frequency, wave number, and finally the pseudoscalar coupling. We apply the results to the first consistent calculations of the mixing of light propagating in a background magnetic field of varying direction, which shows a great variety of fascinating resonant and polarization effects.For about 20 years the mixing of light and pseudoscalar fields in propagation has been studied with fascination [1]- [7]. The subject generated renewed attention in the context of cosmological observables that can probe exceedingly small couplings [8,9,10,11]. One recent approach proposes that the dimming of supernova light might be explained by transition of light into unobserved pseudoscalar, or 1 "axion," modes [12], although this effect might be limited by observations of radio galaxies [13]. It has also been pointed out that pseudoscalar field can generate magnetic fields due to their coupling with photons [14]. Polarization observables are even more sensitive than intensity: for coupling constants many orders of magnitude too small to cause dimming, the cumulative evolution of phase shifts can generate phenomena clearly violating the Maxwell equations in plasmas [15]. Several laboratory experiments have also sought the spontaneous resonant conversion of dark matter axions to photons, and explored the possibilities of conversion in lab-made magnetic fields.There is a well-established theoretical technology of mixing light with a background magnetic field transverse to propagation. Yet despite long study, we know of no complete solution to the mixing problem depending on every possible variable. And there is no wonder, as there are many dimensionful scales, including the magnitude and direction of background magnetic field, the pseudoscalar mass, plasma frequency, propagation frequency, wave number, and finally the pseudoscalar coupling. By approaching the problem with new methods here, we will be able to survey various limits used in the literature and also present a convincing resolution of the dynamics in a slowly varying background field of arbitrary direction.The basic Lagrangian assumes a pseudoscalar 1 field φ coupled to the electromagnetic field strength F µν by the actionWe include a coupling to a current j µ for completeness. For the purposes of linear propagation the potential V (φ) can be ignored as a small perturbation, and the metric g replaced by a given background form. Certain non-local plasma effects, described by the plasma frequency, Faraday rotation, etc., may also need to be incorporated. By translational symmetry, certain eigenmodes will evolve like e ik i z in propagation over a distance z, where k i are wave numbers to be determined. This is simple and obvious. Yet one...