Where is the COBE maps' non-Gaussianity?

We review our recent claim that there is evidence of non-Gaussianity in the 4 Year COBE DMR data. We present some new results concerning the effect of the galactic cut upon the non-Gaussian signal. These findings imply a localization of the non-Gaussian signal on the Northern galactic hemisphere.Comment: Proceedings of COSMO98 Asiloma

The 4 Year COBE DMR data is non-Gaussian

I review our recent claim that there is evidence of non-Gaussianity in the 4 Year COBE DMR data. I describe the statistic we apply, the result we obtain and make a detailed list of the systematics we have analysed. I finish with a qualitative understanding of what it might be and its implications.Comment: Proceedings of Rome 3K conference, 5 pages, 3 figure

Probing non-Gaussianities on Large Scales in WMAP5 and WMAP7 Data using Surrogates

Probing Gaussianity represents one of the key questions in modern cosmology, because it allows to discriminate between different models of inflation. We test for large-scale non-Gaussianities in the cosmic microwave background (CMB) in a model-independent way. To this end, so-called first and second order surrogates are generated by first shuffling the Fourier phases belonging to the scales not of interest and then shuffling the remaining phases for the length scales under study. Using scaling indices as test statistics we find highly significant signatures for both non-Gaussianities and asymmetries on large scales for the WMAP data of the CMB. We find remarkably similar results when analyzing different ILC-maps based on the WMAP five and seven year data. Such features being independent from the map-making procedure would disfavor the fundamental principle of isotropy as well as canonical single-field slow-roll inflation - unless there is some undiscovered systematic error in the collection or reduction of the CMB data or yet unknown foreground contributions.Comment: 4 pages, 3 figures, to appear in the Proceedings of Moriond Cosmology 201

Application of XFaster power spectrum and likelihood estimator to Planck

We develop the XFaster Cosmic Microwave Background (CMB) temperature and polarization anisotropy power spectrum and likelihood technique for the Planck CMB satellite mission. We give an overview of this estimator and its current implementation and present the results of applying this algorithm to simulated Planck data. We show that it can accurately extract the power spectrum of Planck data for the high-l multipoles range. We compare the XFaster approximation for the likelihood to other high-l likelihood approximations such as Gaussian and Offset Lognormal and a low-l pixel-based likelihood. We show that the XFaster likelihood is not only accurate at high-l, but also performs well at moderately low multipoles. We also present results for cosmological parameter Markov Chain Monte Carlo estimation with the XFaster likelihood. As long as the low-l polarization and temperature power are properly accounted for, e.g., by adding an adequate low-l likelihood ingredient, the input parameters are recovered to a high level of accuracy.Comment: 25 pages, 20 figures, updated to reflect published version: slightly extended account of XFaster technique, added improved plots and minor corrections. Accepted for publication in MNRA

A Bayesian estimate of the skewness of the Cosmic Microwave Background

We propose a formalism for estimating the skewness and angular power spectrum of a general Cosmic Microwave Background data set. We use the Edgeworth Expansion to define a non-Gaussian likelihood function that takes into account the anisotropic nature of the noise and the incompleteness of the sky coverage. The formalism is then applied to estimate the skewness of the publicly available 4 year Cosmic Background Explorer (COBE) Differential Microwave Radiometer data. We find that the data is consistent with a Gaussian skewness, and with isotropy. Inclusion of non Gaussian degrees of freedom has essentially no effect on estimates of the power spectrum, if each $C_\ell$ is regarded as a separate parameter or if the angular power spectrum is parametrized in terms of an amplitude (Q) and spectral index (n). Fixing the value of the angular power spectrum at its maxiumum likelihood estimate, the best fit skewness is S=6.5\pm6.0\times10^4(\muK)^3; marginalizing over Q the estimate of the skewness is S=6.5\pm8.4\times10^4(\muK)^3 and marginalizing over n one has S=6.5\pm8.5\times10^4(\muK)^3.Comment: submitted to Astrophysical Journal Letter

Systematic Distortion in Cosmic Microwave Background Maps

To minimize instrumentally induced systematic errors, cosmic microwave background (CMB) anisotropy experiments measure temperature differences across the sky using paires of horn antennas, temperature map is recovered from temperature differences obtained in sky survey through a map-making procedure. To inspect and calibrate residual systematic errors in recovered temperature maps is important as most previous studies of cosmology are based on these maps. By analyzing pixel-ring couping and latitude dependence of CMB temperatures, we find notable systematic deviation from CMB Gaussianity in released Wilkinson Microwave Anisotropy Probe (WMAP) maps. The detected deviation is hard to explain by any process in the early universe and can not be ignored for a precision cosmology study.Comment: accepted for publication in Sci China G-Phy Mech Astro

Interplay between pairing and correlations in spin-polarized bound states

We investigate the single and multiple defects embedded in a superconducting host, studying interplay between the proximity induced pairing and interactions. We explore influence of the spin-orbit coupling on energies, polarization and spatial patterns of the bound (Yu-Shiba-Rusinov) states of magnetic impurities in 2-dimensional square lattice. We also address the peculiar bound states in the proximitized Rashba chain, resembling the Majorana quasiparticles, focusing on their magnetic polarization which has been recently reported by S. Jeon et al., [Science 358, 772 (2017)]. Finally, we study leakage of these polarized Majorana quasiparticles on the side-attached nanoscopic regions and confront them with the subgap Kondo effect near to the singlet-doublet phase transition.Comment: 10 pages, 9 figure