1,154 research outputs found
The Impact of Prior Assumptions on Bayesian Estimates of Inflation Parameters and the Expected Gravitational Waves Signal from Inflation
There has been much recent discussion, and some confusion, regarding the use
of existing observational data to estimate the likelihood that next-generation
cosmic microwave background (CMB) polarization experiments might detect a
nonzero tensor signal, possibly associated with inflation. We examine this
issue in detail here in two different ways: (1) first we explore the effect of
choice of different parameter priors on the estimation of the tensor-to-scalar
ratio r and other parameters describing inflation, and (2) we examine the
Bayesian complexity in order to determine how effectively existing data can
constrain inflationary parameters. We demonstrate that existing data are not
strong enough to render full inflationary parameter estimates in a
parametrization- and prior-independent way and that the predicted tensor signal
is particularly sensitive to different priors. For parametrizations where the
Bayesian complexity is comparable to the number of free parameters we find that
a flat prior on the scale of inflation (which is to be distinguished from a
flat prior on the tensor-to-scalar ratio) leads us to infer a larger, and in
fact slightly nonzero tensor contribution at 68% confidence level. However, no
detection is claimed. Our results demonstrate that all that is statistically
relevant at the current time is the (slightly enhanced) upper bound on r, and
we stress that the data remain consistent with r = 0.Comment: 9 pages, 5 figures. Section added on Bayesian complexity. Matches
published versio
Problems and hopes in nonsymmetric gravity
We consider the linearized nonsymmetric theory of gravitation (NGT) within
the background of an expanding universe and near a Schwarzschild mass. We show
that the theory always develops instabilities unless the linearized
nonsymmetric lagrangian reduces to a particular simple form. This form contains
a gauge invariant kinetic term, a mass term for the antisymmetric metric-field
and a coupling with the Ricci curvature scalar. This form cannot be obtained
within NGT. Based on the linearized lagrangian we know to be stable, we
consider the generation and evolution of quantum fluctuations of the
antisymmetric gravitational field (B-field) from inflation up to the present
day. We find that a B-field with a mass m ~ 0.03(H_I/10^(13)GeV)^4 eV is an
excellent dark matter candidate.Comment: 9 pages, 1 figure. Based on two talks by the authors at the 2nd
International Conference on Quantum Theories and Renormalization Group in
Gravity and Cosmology (IRGAC) 2006, Barcelon
Modeling growth of mandibles in the Western Arctic caribou herd
We compared growth curves for ramus length and diastema length from two autumn collections of mandibles of male Western Arctic Herd caribou in Alaska. We were primarily interested in determining if growth curves of caribou mandibles differed between caribou born during 1959-1967, after the herd had been high for several years and was probably declining in size, and those born during 1976-1988, when the herd was increasing in size. To compare these growth curves, we used a nonlinear model and used maximum likelihood estimates and likelihood ratio tests. We found that growth rates were similar between periods, but intercepts and variances of growth curves differed. From this we infer that calves were smaller in autumn during the 1960s and that significant compensatory growth did not occur later in life
Huntsman: Integrity, Ethics Will be Emphasized in New USU Hall
The shoveling of ceremonial dirt for Utah State University’s new Huntsman Hall was only a formality. The seeds were planted years ago for a bigger, better Jon M. Huntsman School of Business.https://digitalcommons.usu.edu/huntsman_news/1144/thumbnail.jp
The Social Media Disorder Scale
AbstractThere is growing evidence that social media addiction is an evolving problem, particularly among adolescents. However, the absence of an instrument measuring social media addiction hinders further development of the research field. The present study, therefore, aimed to test the reliability and validity of a short and easy to administer Social Media Disorder (SMD) Scale that contains a clear diagnostic cut-off point to distinguish between disordered (i.e. addicted) and high-engaging non-disordered social media users.Three online surveys were conducted among a total of 2198 Dutch adolescents aged 10 to 17. The 9-item scale showed solid structural validity, appropriate internal consistency, good convergent and criterion validity, sufficient test-retest reliability, and satisfactory sensitivity and specificity. In sum, this study generated evidence that the short 9-item scale is a psychometrically sound and valid instruments to measure SMD
Low-speed impact craters in loose granular media
We report on craters formed by balls dropped into dry, non-cohesive, granular
media. By explicit variation of ball density , diameter , and
drop height , the crater diameter is confirmed to scale as the 1/4 power of
the energy of the ball at impact:
. Against expectation, a different
scaling law is discovered for the crater depth:
. The scaling with properties of
the medium is also established. The crater depth has significance for granular
mechanics in that it relates to the stopping force on the ball.Comment: experiment; 4 pages, 3 figure
Case history of the Fortymile Caribou Herd, 1920-1990
Early this century, the Fortymile caribou herd was the largest in Alaska and one of the largest in the world. Since the 1940s the herd has remained relatively small, fluctuating between 6000-8000 and about 50 000. To determine possible limiting factors, we reviewed historical fluctuations in herd since and harvest, historical data on wolf numbers and summer and winter weather. The major decline in herd size from 1963 to 1973 was accompanied by high wolf numbers, some years of unfavorable winter and summer weather, and some years of high harvests. From 1974 to 1990 the Fortymile herd failed to recover as well as the adjacent Nelchi-na herd and provided less than one-fourth the harvest despite favorable winter conditions in both areas. Two notable differences between these herds were that (1) wolves were less strongly limited within the range of the Fortymile herd, and (2) moose as alternate prey for wolves remained more abundant within the range of the Nelchina herd
Transvaginal endoscopy and small ovarian endometriomas: unravelling the missing link?
The incidence of endometriosis in the infertile female is estimated to be between 20 and 50 %. Although the causal relationship between endometriosis and infertility has not been proven, it is generally accepted that the disease impairs reproductive outcome. Indirect imaging techniques and transvaginal laparoscopy now offer the possibility of an early stage diagnosis. Although it remains debated whether the disease is progressive, treatment in an early stage is recommendable as it carries less risk for ovarian damage, hence premature ovarian failure. Under water, inspection with the technique of transvaginal hydrolaparoscopy (THL) accurately shows the invagination of the ovarian cortex as minimal superficial lesions but with the presence of well-differentiated endometrial like tissue at the base, the lateral walls and especially the inner edges of the small endometrioma. An inflammatory environment is responsible for the formation of connecting adhesions with the broad ligament and lateral wall with invasion of endometrial-like tissue and formation of adenomyotic lesions. In around 50 % of the small endometriomas, adhesiolysis is necessary at the site of invagination with opening of the cyst, to free the chocolate content and hereby recognize the underlying endometrioma. The detailed inspection of these early-stage endometriotic lesions at THL reunites the hypothesis of Sampson with the observation of Hughesdon
Vacuum properties of nonsymmetric gravity in de Sitter space
We consider quantum effects of a massive antisymmetric tensor field on the
dynamics of de Sitter space-time. Our starting point is the most general,
stable, linearized Lagrangian arising in nonsymmetric gravitational theories
(NGTs), where part of the antisymmetric field mass is generated by the
cosmological term. We construct a renormalization group (RG) improved effective
action by integrating out one loop vacuum fluctuations of the antisymmetric
tensor field and show that, in the limit when the RG scale goes to zero, the
Hubble parameter -- and thus the effective cosmological constant -- relaxes
rapidly to zero. We thus conclude that quantum loop effects in de Sitter space
can dramatically change the infrared sector of the on-shell gravity, making the
expansion rate insensitive to the original (bare) cosmological constant.Comment: 32 pages, 2 eps figure
Instabilities in the nonsymmetric theory of gravitation
We consider the linearized nonsymmetric theory of gravitation (NGT) within
the background of an expanding universe and near a Schwarzschild metric. We
show that the theory always develops instabilities unless the linearized
nonsymmetric lagrangian reduces to a particular simple form. This theory
contains a gauge invariant kinetic term, a mass term for the antisymmetric
metric-field and a coupling with the Ricci curvature scalar. This form cannot
be obtained within NGT. Next we discuss NGT beyond linearized level and
conjecture that the instabilities are not a relic of the linearization, but are
a general feature of the full theory. Finally we show that one cannot add
ad-hoc constraints to remove the instabilities as is possible with the
instabilities found in NGT by Clayton.Comment: 29 page
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