arXiv subjects

P. Naselsky

Publications and source records attributed to P. Naselsky.

13 recordsLinked to original sources

arXiv2024

B-mode polarization forecasts for GreenPol

We present tensor-to-scalar ratio forecasts for GreenPol, a hypothetical ground-based B-mode experiment aiming to survey the cleanest regions of the Northern Galactic Hemisphere at five frequencies between 10 and 44 GHz. Its primary science goal would be to measure large-scale CMB polarization fluctuations at multipoles $\ell \lesssim 500$, and thereby constrain the primordial tensor-to-scalar ratio. The observations for the suggested experiment would take place at the Summit Station (72deg N, 38deg W) on Greenland, at an altitude of 3216 m above sea level. In this paper we simulate various experimental setups, and derive limits on the tensor-to-scalar ratio after CMB component separation using a Bayesian component separation implementation called Commander. When combining the proposed experiment with Planck HFI observations for constraining polarized thermal dust emission, we find a projected limit of r<0.02 at 95 % confidence for the baseline configuration. This limit is very robust with respect to a range of important experimental parameters, including sky coverage, detector weighting, foreground priors etc. Overall, GreenPol would have the possibility to provide deep CMB polarization measurements of the Northern Galactic Hemisphere at low frequencies.

astro-ph.CO↗

arXiv2016

Understanding the LIGO GW150914 event

We present a simplified method for the extraction of meaningful signals from Hanford and Livingstone 32 seconds data for the GW150914 event made publicly available by the LIGO collaboration and demonstrate its ability to reproduce the LIGO collaboration's own results quantitatively given the assumption that all narrow peaks in the power spectrum are a consequence of physically uninteresting signals and can be removed. After the clipping of these peaks and return to the time domain, the GW150914 event is readily distinguished from broadband background noise. This simple technique allows us to identify the GW150914 event without any assumption regarding its physical origin and with minimal assumptions regarding its shape. We also confirm that the LIGO GW150914 event is uniquely correlated in the Hanford and Livingston detectors for 4096 second data at the level of $6-7\,σ$ with a temporal displacement of $τ=6.9 \pm 0.4\,$ms. We have also identified a few events that are morphologically close to GW150914 but less strongly cross correlated with it.

astro-ph.CO↗

arXiv2012

Can residuals of the Solar system foreground explain low multipole anomalies of the CMB ?

The low multipole anomalies of the Cosmic Microwave Background has received much attention during the last few years. It is still not ascertained whether these anomalies are indeed primordial or the result of systematics or foregrounds. An example of a foreground, which could generate some non-Gaussian and statistically anisotropic features at low multipole range, is the very symmetric Kuiper Belt in the outer solar system. In this paper, expanding upon the methods presented by Maris et al. (2011), we investigate the contributions from the Kuiper Belt objects (KBO) to the WMAP ILC 7 map, whereby we can minimize the contrast in power between even and odd multipoles in the CMB, discussed discussed by Kim & Naselsky (2010). We submit our KBO de-correlated CMB signal to several tests, to analyze its validity, and find that incorporation of the KBO emission can decrease the quadrupole-octupole alignment and parity asymmetry problems, provided that the KBO signals has a non-cosmological dipole modulation, associated with the statistical anisotropy of the ILC 7 map. Additionally, we show that the amplitude of the dipole modulation, within a 2 sigma interval, is in agreement with the corresponding amplitudes, discussed by Lew (2008).

astro-ph.CO↗

arXiv2012

Morphology of High-Multiplicity Events in Heavy Ion Collisions

We discuss opportunities that may arise from subjecting high-multiplicity events in relativistic heavy ion collisions to an analysis similar to the one used in cosmology for the study of fluctuations of the Cosmic Microwave Background (CMB). To this end, we discuss examples of how pertinent features of heavy ion collisions including global characteristics, signatures of collective flow and event-wise fluctuations are visually represented in a Mollweide projection commonly used in CMB analysis, and how they are statistically analyzed in an expansion over spherical harmonic functions. If applied to the characterization of purely azimuthal dependent phenomena such as collective flow, the expansion coefficients of spherical harmonics are seen to contain redundancies compared to the set of harmonic flow coefficients commonly used in heavy ion collisions. Our exploratory study indicates, however, that these redundancies may offer novel opportunities for a detailed characterization of those event-wise fluctuations that remain after subtraction of the dominant collective flow signatures. By construction, the proposed approach allows also for the characterization of more complex collective phenomena like higher-order flow and other sources of fluctuations, and it may be extended to the characterization of phenomena of non-collective origin such as jets.

hep-ph↗

arXiv2012

Is the CMB asymmetry due to the kinematic dipole?

Parity violation found in the Cosmic Microwave Background (CMB) radiation is a crucial clue for the non-standard cosmological model or the possible contamination of various foreground residuals and/or calibration of the CMB data sets. In this paper, we study the directional properties of the CMB parity asymmetry by excluding the $m=0$ modes in the definition of parity parameters. We find that the preferred directions of the parity parameters coincide with the CMB kinematic dipole, which implies that the CMB parity asymmetry may be connected with the possible contamination of the residual dipole component. We also find that such tendency is not only localized at $l=2,3$, but in the extended multipole ranges up to $l\sim 22$.

astro-ph.CO↗

arXiv2011

Symmetry of the CMB sky as a new test of its statistical isotropy. Non Cosmological Octupole?

In this article we propose a novel test for statistical anisotropy of the CMB. The test is based on the fact, that the Galactic foregrounds have a remarcably strong symmetry with respect to their antipodal points and with respect to the Galactic plane, while the cosmological signal should not be symmetric or asymmetric under these transitions. We have applied the test for the octupole component of the WMAP ILC 7 map, by looking at a_3,1 and a_3,3, and their ratio to a_3,2 both for real and imaginary values. We find abnormal symmetry of the octupole component at the level of 0.58%, compared to Monte Carlo simulations. By using the analysis of the phases of the octupole we found remarkably strong cross-correlations between the phases of kinematic dipole and ILC 7 octupole, in full agreement with previous results. We further test the multipole range 2<l<100, by investigating the ratio between the l+m=even and l+m=odd parts of power spectra. We compare the results to simulations of a Gaussian random sky, and find significant departure from the statistically isotropic and homogeneous case, for a very broad range of multipoles. We found that for the most prominent peaks of our estimator, the phases of the corresponding harmonics are coherent with phases of the octupole. We believe, our test would be very useful for detections of various types of residuals of the foreground and systematic effects at very a broad range of multipoles 2 < l < 1500-3000 for the forthcoming PLANCK CMB map, before any conclusions about primordial non-Gaussianity and statistical anisotropy of the CMB.

astro-ph.CO↗

arXiv2011

Pearson's random walk in the space of the CMB phases: evidence for parity asymmetry

The temperature fluctuations of the Cosmic Microwave Background (CMB) are supposed to be distributed randomly in both magnitude and phase, following to the simplest model of inflation. In this paper, we look at the odd and even multipoles of the spherical harmonic decomposition of the CMB, and the different characteristics of these, giving rise to a parity asymmetry. We compare the even and odd multipoles in the CMB power spectrum, and also the even and odd mean angles. We find for the multipoles of the power spectrum, that there is power excess in odd multipoles, compared to even ones, meaning that we have a parity asymmetry. Further, for the phases, we present a random walk for the mean angles, and find a significant separation for even/odd mean angles, especially so for galactic coordinates. This is further tested and confirmed with a directional parity test, comparing the parity asymmetry in galactic and ecliptic coordinates.

astro-ph.CO↗

arXiv2001

The primordial baryonic clouds and their contribution to the CMB anisotropy and polarization formation

We discuss possible distortions of the ionization history of the Universe in the model with small scale baryonic clouds. The corresponding scales of the clouds are much smaller than the typical galactic mass scales. These clouds are considered in a framework of the cosmological model with the isocurvature and adiabatic perturbations. In this model the baryonic clouds do not influence on the cosmic microwave background anisotropy formation directly as an additional sources of perturbations, but due to change of the kinetics of the hydrogen recombination . We also study the corresponding distortions of the anisotropy and polarization power spectra in connection with the launched MAP and future PLANCK missions.

astro-ph↗

arXiv2000

Estimation of Signal and Noise Parameters from CMB Polarization Observations

We propose a technique for determination of the spectral parameters of the cosmological signal and pixel noise using observational data on CMB polarization without any additional assumptions. We introduce the notion of so called crossing points in the observational maps and derive the theoretical dependence of the total number of crossing points at different level of the polarization. Finally, we use the statistics of the signal in the vicinities of the singular points, where the polarization of the pure CMB vanishes to correct the final result.

astro-ph↗

arXiv2000

Peculiarities of anisotropy and polarization as an indicator of noises in the CMB maps

We discuss some new problems of the modern cosmology which arose after the BOOMERANG and MAXIMA-1 successful missions. Statistics of high peaks of the CMB anisotropy is analyzed and we discuss possible inner structure of such peaks in the observational data of future MAP and PLANCK missions. We have investigated geometrical and statistical properties of the CMB polarization around such high isolated peaks of anisotropy in the presence of a polarized pixel noise and point sources. The structure of polarization fields in the vicinity of singular points with zero polarization is very sensitive to the level of pixel noises and point sources in the CMB maps.

astro-ph↗

arXiv2000

Amplitude-Phase Analysis of Cosmic Microwave Background maps

We propose a novel method for the extraction of unresolved point sources from CMB maps. This method is based on the analysis of the phase distribution of the Fourier components for the observed signal and unlike most other methods of denoising does not require any significant assumptions about the expected CMB signal. The aim of our paper is to show how, using our algorithm, the contribution from point sources can be separated from the resulting signal on all scales. We believe that this technique is potentially a very powerful tool for extracting this type of noise from future high resolution maps.

astro-ph↗

arXiv2000

Power filtration of CMB observational data

We propose a power filter Gp for linear reconstruction of the CMB signal from observational maps. This Gp filter preserves the power spectrum of the CMB signal in contrast to the Wiener filter which diminishes the power spectrum of the reconstructed CMB signal. We demonstrate how peak statistics and a cluster analysis can be used to estimate the probability of the presence of a CMB signal in observational records. The efficiency of the Gp filter is demonstrated on a toy model of an observational record consisting of a CMB signal and noise in the form of foreground point sources.

astro-ph↗

arXiv1998

Blue spectra and induced formation of primordial black holes

We investigate the statistical properties of primordial black hole (PBH) formation in the very early Universe. We show that the high level of inhomogeneity of the early Universe leads to the formation of the first generation PBHs. %The existence of these PBHs This causes later the appearance of a dust-like phase of the cosmological expansion. We discuss here a new mechanism for the second generation of PBH formation during the dust-like phase. This mechanism is based on the coagulation process. We demonstrate that the blue power spectrum of initial adiabatic perturbations after inflation leads to overproduction of primordial black holes with $10^9$g$\le M\le10^{15}$g if the power index is $n\ge1.2$.

astro-ph↗