576 research outputs found
Using Big Bang Nucleosynthesis to Extend CMB Probes of Neutrino Physics
We present calculations showing that upcoming Cosmic Microwave Background
(CMB) experiments will have the power to improve on current constraints on
neutrino masses and provide new limits on neutrino degeneracy parameters. The
latter could surpass those derived from Big Bang Nucleosynthesis (BBN) and the
observationally-inferred primordial helium abundance. These conclusions derive
from our Monte Carlo Markov Chain (MCMC) simulations which incorporate a full
BBN nuclear reaction network. This provides a self-consistent treatment of the
helium abundance, the baryon number, the three individual neutrino degeneracy
parameters and other cosmological parameters. Our analysis focuses on the
effects of gravitational lensing on CMB constraints on neutrino rest mass and
degeneracy parameter. We find for the PLANCK experiment that total (summed)
neutrino mass eV could be ruled out at or better.
Likewise neutrino degeneracy parameters and could be detected or ruled out at
confidence, or better. For POLARBEAR we find that the corresponding detectable
values are , , and , while for EPIC we obtain ,
, and . Our forcast for
EPIC demonstrates that CMB observations have the potential to set constraints
on neutrino degeneracy parameters which are better than BBN-derived limits and
an order of magnitude better than current WMAP-derived limits.Comment: 27 pages, 11 figures, matches published version in JCA
CMB Polarization Systematics Due to Beam Asymmetry: Impact on Cosmological Birefringence
The standard cosmological model is assumed to respect parity symmetry. Under
this assumption the cross-correlations of the CMB's temperature anisotropy and
`gradient'-like polarization, with the `curl'-like polarization identically
vanish over the full sky. However, extensions of the standard model which allow
for light scalar field or axion coupling to the electromagnetic field, or
coupling to the Riemann gravitational field-strength, as well as other
modifications of field theories, may induce a rotation of the CMB polarization
plane on cosmological scales and manifest itself as nonvanishing TB and EB
cross-correlations. Recently, the degree of parity violation (reflected in
polarization rotation) was constrained using data from BOOMERANG, WMAP and
QUAD. Forecasts have been made for near-future experiments (e.g. PLANCK) to
further constrain parity- and Lorentz-violating terms in the fundamental
interactions of nature. Here we consider a real-world effect induced by a class
of telescope beam systematics which can mimic the rotation of polarization
plane or otherwise induce nonvanishing TB and EB correlations. In particular,
adopting the viewpoint that the primary target of future experiments will be
the inflationary B-mode signal, we assume the beam-systematics of the upcoming
PLANCK and POLARBEAR experiments are optimized towards this goal, and explore
the implications of the allowed levels of beam systematics on the resulting
precision of polarization-rotation measurements.Comment: 9 pages. Minor typos corrected. Matches published version in PRD Vol.
79 No. 1
The Effects of Game Size on the Physical Activity Levels and Ball Touches of Elementary School Children in Physical Education
The purpose of this study was to determine the impact of participating in small (3v3), medium (6v6), and large-sided (12v12) games on the physical activity levels (pedometer step counts, accelerometer counts, and minutes of moderate-to-vigorous physical activity) and ball touches of children in physical education class. Participants were 29 students (55% boys and 45% girls) age 10-11 yrs. All participants wore a Yamax SW-200 pedometer and had their ball touches monitored and recorded. Twelve participants also wore an ActiGraph GT3X accelerometer. Repeated measure ANOVAs were computed to test for significant differences for each dependant variable with corresponding post hoc tests. Results indicated the 3v3 and 6v6 game conditions yielded significantly higher accelerometer counts and ball touches than the 12v12 condition. The 3v3 game condition also produced significantly higher ball touches than the 6v6 condition. These findings highlight the importance of utilizing smaller-sided games in physical education to promote increased involvement and physical activity
Revealing Cosmic Rotation
Cosmological Birefringence (CB), a rotation of the polarization plane of
radiation coming to us from distant astrophysical sources, may reveal parity
violation in either the electromagnetic or gravitational sectors of the
fundamental interactions in nature. Until only recently this phenomenon could
be probed with only radio observations or observations at UV wavelengths.
Recently, there is a substantial effort to constrain such non-standard models
using observations of the rotation of the polarization plane of cosmic
microwave background (CMB) radiation. This can be done via measurements of the
-modes of the CMB or by measuring its TB and EB correlations which vanish in
the standard model. In this paper we show that correlations-based
estimator is the best for upcoming polarization experiments. The based
estimator surpasses other estimators because it has the smallest noise and of
all the estimators is least affected by systematics. Current polarimeters are
optimized for the detection of -mode polarization from either primordial
gravitational waves or by large scale structure via gravitational lensing. In
the paper we also study optimization of CMB experiments for the detection of
cosmological birefringence, in the presence of instrumental systematics, which
by themselves are capable of producing correlations; potentially mimicking
CB.Comment: 10 pages, 3 figures, 2 table
Constraints on the Neutrino Mass from SZ Surveys
Statistical measures of galaxy clusters are sensitive to neutrino masses in
the sub-eV range. We explore the possibility of using cluster number counts
from the ongoing PLANCK/SZ and future cosmic-variance-limited surveys to
constrain neutrino masses from CMB data alone. The precision with which the
total neutrino mass can be determined from SZ number counts is limited mostly
by uncertainties in the cluster mass function and intracluster gas evolution;
these are explicitly accounted for in our analysis. We find that projected
results from the PLANCK/SZ survey can be used to determine the total neutrino
mass with a (1\sigma) uncertainty of 0.06 eV, assuming it is in the range
0.1-0.3 eV, and the survey detection limit is set at the 5\sigma significance
level. Our results constitute a significant improvement on the limits expected
from PLANCK/CMB lensing measurements, 0.15 eV. Based on expected results from
future cosmic-variance-limited (CVL) SZ survey we predict a 1\sigma uncertainty
of 0.04 eV, a level comparable to that expected when CMB lensing extraction is
carried out with the same experiment. A few percent uncertainty in the mass
function parameters could result in up to a factor \sim 2-3 degradation of our
PLANCK and CVL forecasts. Our analysis shows that cluster number counts provide
a viable complementary cosmological probe to CMB lensing constraints on the
total neutrino mass.Comment: Replaced with a revised version to match the MNRAS accepted version.
arXiv admin note: text overlap with arXiv:1009.411
Cosmic Microwave Background Temperature at Galaxy Clusters
We have deduced the cosmic microwave background (CMB) temperature in the Coma
cluster (A1656, ), and in A2163 () from spectral
measurements of the Sunyaev-Zel'dovich (SZ) effect over four passbands at radio
and microwave frequencies. The resulting temperatures at these redshifts are
K and K, respectively. These values confirm the expected
relation , where K is the value
measured by the COBE/FIRAS experiment. Alternative scaling relations that are
conjectured in non-standard cosmologies can be constrained by the data; for
example, if or , then
and (at 95% confidence). We
briefly discuss future prospects for more precise SZ measurements of at
higher redshifts.Comment: 13 pages, 1 figure, ApJL accepted for publicatio
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