5,169 research outputs found
Template fitting and the large-angle CMB anomalies
We investigate two possible explanations for the large-angle anomalies in the
Cosmic Microwave Background (CMB): an intrinsically anisotropic model and an
inhomogeneous model. We take as an example of the former a Bianchi model (which
leaves a spiral pattern in the sky) and of the latter a background model that
already contains a non-linear long-wavelength plane wave (leaving a stripy
pattern in the sky). We make use of an adaptation of the ``template''
formalism, previously designed to detect galactic foregrounds, to recognize
these patterns and produce confidence levels for their detection. The
``corrected'' maps, from which these patterns have been removed, are free of
anomalies, in particular their quadrupole and octupole are not planar and their
intensities not low. We stress that although the ``template'' detections are
not found to be statistically significant they do correct statistically
significant anomalies.Comment: 8 pages. MNRAS submitte
Multipole invariants and non-Gaussianity
We propose a framework for separating the information contained in the CMB
multipoles, , into its algebraically independent components. Thus
we cleanly separate information pertaining to the power spectrum,
non-Gaussianity and preferred axis effects. The formalism builds upon the
recently proposed multipole vectors (Copi, Huterer & Starkman 2003; Schwarz &
al 2004; Katz & Weeks 2004), and we elucidate a few features regarding these
vectors, namely their lack of statistical independence for a Gaussian random
process. In a few cases we explicitly relate our proposed invariants to
components of the -point correlation function (power spectrum, bispectrum).
We find the invariants' distributions using a mixture of analytical and
numerical methods. We also evaluate them for the co-added WMAP first year map
The Multipole Vectors of WMAP, and their frames and invariants
We investigate the Statistical Isotropy and Gaussianity of the CMB
fluctuations, using a set of multipole vector functions capable of separating
these two issues. In general a multipole is broken into a frame and
ordered invariants. The multipole frame is found to be suitably sensitive to
galactic cuts. We then apply our method to real WMAP datasets; a coadded masked
map, the Internal Linear Combinations map, and Wiener filtered and cleaned
maps. Taken as a whole, multipoles in the range or show
consistency with statistical isotropy, as proved by the Kolmogorov test applied
to the frame's Euler angles. This result in {\it not} inconsistent with
previous claims for a preferred direction in the sky for . The
multipole invariants also show overall consistency with Gaussianity apart from
a few anomalies of limited significance (98%), listed at the end of this paper.Comment: 9 pages. Submitted to MNRA
Teachers Perception of Leadership Styles, Institutional Factors and Principal Demographics Related to Teacher Attrition on Suburban Middle School Campuses
The shortage of teachers in the country is staggering (Shuls & Flores, 2020). According to UNESCO Institute for Statistics (2022), teacher shortages widen the equity gap in education; therefore, it is essential to assess and monitor
teacher attrition. This study added to the body of knowledge relating to teacher attrition by exploring the predictive relationship between attrition and instructional factors, principal demographics, and leadership styles as perceived by teachers. The study focused on suburban middle school teachers and their perception of attrition which was the dependent variable. The three independent variable sets were: principal leadership styles (transactional, transformational, Laissez-faire, and authoritarian) and other leadership demographic factors, institutional factors (Title I versus Non-Title I campus) and classroom factors (class size, discipline, subject taught). This study will add to the body of knowledge and benefit principals, human resources (HR) staff, and teachers
The Axis of Evil revisited
In light of the three-year data release from WMAP we re-examine the evidence
for the ``Axis of Evil'' (AOE). We discover that previous statistics are not
robust with respect to the data-sets available and different treatments of the
galactic plane. We identify the cause of the instability and implement an
alternative ``model selection'' approach. A comparison to Gaussian isotropic
simulations find the features significant at the 94-98% level, depending on the
particular AOE model. The Bayesian evidence finds lower significance, ranging
from ``substantial'' at , to no evidence for the most
general AOE model.Comment: 7 pages, accepted to MNRA
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