887 research outputs found
Constraining neutrino masses with the ISW-galaxy correlation function
Temperature anisotropies in the Cosmic Microwave Background (CMB) are
affected by the late Integrated Sachs-Wolfe (lISW) effect caused by any
time-variation of the gravitational potential on linear scales. Dark energy is
not the only source of lISW, since massive neutrinos induce a small decay of
the potential on small scales during both matter and dark energy domination. In
this work, we study the prospect of using the cross-correlation between CMB and
galaxy density maps as a tool for constraining the neutrino mass. On the one
hand massive neutrinos reduce the cross-correlation spectrum because
free-streaming slows down structure formation; on the other hand, they enhance
it through their change in the effective linear growth. We show that in the
observable range of scales and redshifts, the first effect dominates, but the
second one is not negligible. We carry out an error forecast analysis by
fitting some mock data inspired by the Planck satellite, Dark Energy Survey
(DES) and Large Synoptic Survey Telescope (LSST). The inclusion of the
cross-correlation data from Planck and LSST increases the sensitivity to the
neutrino mass m_nu by 38% (and to the dark energy equation of state w by 83%)
with respect to Planck alone. The correlation between Planck and DES brings a
far less significant improvement. This method is not potentially as good for
detecting m_nu as the measurement of galaxy, cluster or cosmic shear power
spectra, but since it is independent and affected by different systematics, it
remains potentially interesting if the total neutrino mass is of the order of
0.2 eV; if instead it is close to the lower bound from atmospheric
oscillations, m_nu ~ 0.05 eV, we do not expect the ISW-galaxy correlation to be
ever sensitive to m_nu.Comment: 10 pages, 8 figures. References added. Accepted for publication in
Phys.Rev.
New constraints on the observable inflaton potential from WMAP and SDSS
We derive some new constraints on single-field inflation from the Wilkinson
Microwave Anisotropy Probe 3-year data combined with the Sloan Luminous Red
Galaxy survey. Our work differs from previous analyses by focusing only on the
observable part of the inflaton potential, or in other words, by making
absolutely no assumption about extrapolation of the potential from its
observable region to its minimum (i.e., about the branch of the potential
responsible for the last ~50 inflationary e-folds). We only assume that
inflation starts at least a few e-folds before the observable Universe leaves
the Hubble radius, and that the inflaton rolls down a monotonic and regular
potential, with no sharp features or phase transitions. We Taylor-expand the
inflaton potential at order v=2, 3 or 4 in the vicinity of the pivot scale,
compute the primordial spectra of scalar and tensor perturbations numerically
and fit the data. For v>2, a large fraction of the allowed models is found to
produce a large negative running of the scalar tilt, and to fall in a region of
parameter space where the second-order slow-roll formalism is strongly
inaccurate. We release a code for the computation of inflationary perturbations
which is compatible with CosmoMC.Comment: 10 pages, 6 figures, codes available at
http://wwwlapp.in2p3.fr/~lesgourgues/inflation/. Version to be published in
Phys.Rev.
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
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
Impaired glucose tolerance and diabetes mellitus in a rural population in South India
In the present study the prevalence of impaired glucose tolerance and non-insulin dependent diabetes mellitus in a rural population in South India was assessed and its associations with body mass index and a family history of diabetes mellitus. Data were obtained from inhabitants of two villages located in the North Arcot District of Tamil Nadu. After an overnight fast, 467 randomly selected subjects, aged 40 years or over, were given 75 g glucose orally. After two hours the capillary glucose level was determined. The prevalence of impaired glucose tolerance (2 h value ≥ 7.8 mmol/l and < 11.1 mmol/l) was 6.6% (31 subjects). Non-insulin dependent diabetes mellitus (2 h value ≥ 11.1 mmol/l) was found in 23 subjects (4.9%). Of these, 53% were previously unknown. Age and sex adjusted mean body mass index was significantly higher among subjects with impaired glucose tolerance compared to subjects without glucose intolerance, with a mean difference of 1.4 kg/m2 (95% confidence interval (CI) 0.2, 2.6). A positive family history of diabetes was non-significantly higher in subjects with impaired glucose tolerance. Subjects with non-insulin-dependent diabetes mellitus had a higher mean body mass index compared to subjects with normal glucose levels with a mean difference of 1.9 kg/m2 (95% CI 0.5, 3.3). A positive family history of diabetes was more common among diabetics with a difference of 20% (95% CI 10, 30). Our findings suggest that in a considerable proportion (11.5%) of the rural South Indian population aged 40 years or over glucose intolerance is present. These results may indicate that apart from other important causes of morbidity and mortality, a substantial proportion of the rural Indian population will suffer from cardiovascular morbidity and mortality in the near future
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
Constraining Inflation
Slow roll reconstruction is derived from the Hamilton-Jacobi formulation of
inflationary dynamics. It automatically includes information from sub-leading
terms in slow roll, and facilitatesthe inclusion of priors based on the
duration on inflation. We show that at low inflationary scales the
Hamilton-Jacobi equations simplify considerably. We provide a new
classification scheme for inflationary models, based solely on the number of
parameters needed to specify the potential, and provide forecasts for likely
bounds on the slow roll parameters from future datasets. A minimal running of
the spectral index, induced solely by the first two slow roll parameters
(\epsilon and \eta) appears to be effectively undetectable by realistic Cosmic
Microwave Background experiments. However, we show that the ability to detect
this signal increases with the lever arm in comoving wavenumber, and we
conjecture that high redshift 21 cm data may allow tests of second order
consistency conditions on inflation. Finally, we point out that the second
order corrections to the spectral index are correlated with the inflationary
scale, and thus the amplitude of the CMB B-mode.Comment: 32 pages. v
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
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