arXiv subjects

Pramoda Kumar Samal

Publications and source records attributed to Pramoda Kumar Samal.

6 recordsLinked to original sources

arXiv2020

Parity in Planck full-mission CMB temperature maps

In the standard model of cosmology, Cosmic Microwave Background (CMB) sky is expected to show no symmetry preferences. Following our previous studies, we explore the presence of any particular parity preference in the latest full-mission CMB temperature maps from ESA's Planck probe. Specifically, in this work, we will probe (a)symmetry in power between even and odd multipoles of CMB via it's angular power spectrum from Planck 2015 data. Further we also assess any specific preference for mirror parity (a)symmetry, by analysing the power contained in $l+m$=even or odd mode combinations.

astro-ph.CO↗

arXiv2017

Testing isotropy of cosmos with WMAP and PLANCK data

In recent years, there have been a large number of studies which support violation of statistical isotropy. Meanwhile, there are some studies which also found inconsistency. We use the power tensor method defined earlier in the literature to study the new CMBR data. The orientation of these three orthogonal vectors, as well as the power associated with each vector, contains information about possible violation of statistical isotropy. This information is encoded in two entropy measures, the power-entropy and alignment- entropy. We apply this method to WMAP 9-year and PLANCK data. Here, we also revisit the statistics to test high-l anomaly reported in our earlier paper and find that the high degree of isotropy seen in earlier WMAP 5-year data is absent in the revised WMAP 9-year data.

astro-ph.CO↗

arXiv2013

Energy levels of an anharmonic oscillator in both weak and strong coupling limit using convergency of Morse-Feshbach non-linear perturbation series

We make an extensive rigorous study on convergent behaviour of Morse-Feshbach nonlinear perturbation series (MFNPS) to find out energy levels of the anharmonic oscillator (AHO) in both weak and strong coupling limit. We develop a new method of multi step optimal splitting in order to get convergency in MFNPS for ground state of AHO and found that two step optimal splitting is sufficient to provide convergency in MFNPS. Unlike the ground state the optimal splitting parameters for excited states is modified according to their dependency on state in order to achieve convergency in MFNPS.

quant-ph↗

arXiv2009

CMB Polarization and Temperature Power Spectra Estimation using Linear Combination of WMAP 5-year Maps

We estimate CMB polarization and temperature power spectra using WMAP 5-year foreground contaminated maps. The power spectrum is estimated by using a model independent method, which does not utilize directly the diffuse foreground templates nor the detector noise model. The method essentially consists of two steps, (i) removal of diffuse foregrounds contamination by making linear combination of individual maps in harmonic space and (ii) cross-correlation of foreground cleaned maps to minimize detector noise bias. For temperature power spectrum we also estimate and subtract residual unresolved point source contamination in the cross-power spectrum using the point source model provided by the WMAP science team. Our $TT$, $TE$ and $EE$ power spectra are in good agreement with the published results of the WMAP science team. The error bars on the polarization power spectra, however, turn out to be smaller in comparison to what is obtained by the WMAP science team. We perform detailed numerical simulations to test for bias in our procedure. We find that the bias is small in all cases. A negative bias at low $l$ in $TT$ power spectrum has been pointed in an earlier publication. We find that the bias corrected quadrupole power ($l(l+1)C_l/2π)$ is 532 $μK^2$, approximately 2.5 times the estimate (213.4 $μK^2$) made by the WMAP team.

astro-ph.CO↗

arXiv2008

Signals of Statistical Anisotropy in WMAP Foreground-Cleaned Maps

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-year and 5-year WMAP-$DA$ maps. We examine a wide range of angular multipoles from $2 < l < 300$. The analysis detects statistically signicant signals of anisotropy inconsistent with an isotropic CMB 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 modeling of detector noise.

astro-ph↗

arXiv2007

Testing Isotropy of Cosmic Microwave Background Radiation

We introduce new symmetry-based methods to test for isotropy in cosmic microwave background radiation. Each angular multipole is factored into unique products of power eigenvectors, related multipoles and singular values that provide 2 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, and the new procedures mesh perfectly with linear transformations employed for windowed-sky analysis. The ILC -WMAP data maps show 7 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% probability or lower in an isotropic distribution. Isotropy of the ILC maps is ruled out to confidence levels of better than 99.9%, 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.

astro-ph↗