1,738 research outputs found
On prospects for dark matter indirect detection in the Constrained MSSM
In the framework of the Constrained MSSM we derive the most probable ranges of the diffuse gamma radiation flux from the direction of the Galactic center and of the positron flux from the Galactic halo due to neutralino dark matter annihilation. We find that, for a given halo model, and assuming flat priors, the 68% probability range of the integrated gamma-ray flux spans about one order of magnitude, while the 95% probability range can be much larger and extend over four orders of magnitude (even exceeding five for a tiny region at small neutralino mass). The detectability of the signal by GLAST depending primarily on the cuspiness of the halo profile. The positron flux, on the other hand, appears to be too small to be detectable by PAMELA, unless the boost factor is at least of order ten and/or the halo profile is extremely cuspy. We also briefly discuss the sensitivity of our results to the choice of priors
The power of Bayesian evidence in astronomy
We discuss the use of the Bayesian evidence ratio, or Bayes factor, for model
selection in astronomy. We treat the evidence ratio as a statistic and
investigate its distribution over an ensemble of experiments, considering both
simple analytical examples and some more realistic cases, which require
numerical simulation. We find that the evidence ratio is a noisy statistic, and
thus it may not be sensible to decide to accept or reject a model based solely
on whether the evidence ratio reaches some threshold value. The odds suggested
by the evidence ratio bear no obvious relationship to the power or Type I error
rate of a test based on the evidence ratio. The general performance of such
tests is strongly affected by the signal to noise ratio in the data, the
assumed priors, and the threshold in the evidence ratio that is taken as
`decisive'. The comprehensiveness of the model suite under consideration is
also very important. The usefulness of the evidence ratio approach in a given
problem can be assessed in advance of the experiment, using simple models and
numerical approximations. In many cases, this approach can be as informative as
a much more costly full-scale Bayesian analysis of a complex problem.Comment: 11 pages; MNRAS in pres
INCREASING EFFICIENCY OF FINISHING BEEF PRODUCTION: STRATEGIES TO OPTIMIZE STARCH DIGESTION, IMPROVE FLAKE QUALITY, AND REDUCE METHANE EMISSIONS
To continue to meet the demands of increasing food production and environmental sustainability, new strategies are needed to enhance the efficiency of finishing cattle production. A review of the literature identified several nutritional and physiological constraints that limit the ability for cattle to digest starch and absorb glucose from the small intestine. Comparative sequencing analyses revealed a missing region of the sucrase-isomaltase protein which could affect the capacity for starch digestion in cattle. Post-flaking sampling and handling recommendations were generated based on a series of experiments to improve estimates of starch availability and flaking consistency for commercial feedlots and laboratories. Increasing flake density and increasing starch retrogradation could potentially be implemented as processing strategies to shift the site of starch digestion to the small intestine and reduce substrate available for ruminal methanogenesis. For smaller cattle feeders where flaking corn is not an option, low to moderate inclusion of fine-ground corn in finishing rations might be a suitable processing alternative. Feeding anti-coccidial compounds with saponins did not decrease methane production; yet, future attempts to replace antibiotics in finishing cattle diets should attempt to replace the anti-coccidial and anti-methanogenic activity of ionophores. A novel, in vivo animal model was developed to selectively target increased endogenous pancreatic and/or small intestinal carbohydrase activities to evaluate physiological mechanisms to increase small intestinal starch digestion. Next-generation RNA sequencing revealed that exogenous glucagon-like peptide 2 administration affected several metabolic pathways and molecular functions of the jejunal mucosa, which could potentially improve growth, health, and feed efficiency of feedlot cattle. These findings could be used to further develop strategies to optimize starch digestion, improve flake quality, and reduce methane emissions of finishing beef cattle
Quantifying the tension between the Higgs mass and (g-2)_mu in the CMSSM
Supersymmetry has been often invoqued as the new physics that might reconcile
the experimental muon magnetic anomaly, a_mu, with the theoretical prediction
(basing the computation of the hadronic contribution on e^+ e^- data). However,
in the context of the CMSSM, the required supersymmetric contributions (which
grow with decreasing supersymmetric masses) are in potential tension with a
possibly large Higgs mass (which requires large stop masses). In the limit of
very large m_h supersymmetry gets decoupled, and the CMSSM must show the same
discrepancy as the SM with a_mu . But it is much less clear for which size of
m_h does the tension start to be unbearable. In this paper, we quantify this
tension with the help of Bayesian techniques. We find that for m_h > 125 GeV
the maximum level of discrepancy given current data (~ 3.3 sigma) is already
achieved. Requiring less than 3 sigma discrepancy, implies m_h < 120 GeV. For a
larger Higgs mass we should give up either the CMSSM model or the computation
of a_mu based on e^+ e^-; or accept living with such inconsistency
Directional Detection of Dark Matter with MIMAC
Directional detection is a promising search strategy to discover galactic
Dark Matter. We present a Bayesian analysis framework dedicated to Dark Matter
phenomenology using directional detection. The interest of directional
detection as a powerful tool to set exclusion limits, to authentify a Dark
Matter detection or to constrain the Dark Matter properties, both from particle
physics and galactic halo physics, will be demonstrated. However, such results
need highly accurate track reconstruction which should be reachable by the
MIMAC detector using a dedicated readout combined with a likelihood analysis of
recoiling nuclei.Comment: 4 pages, 2 figures, to appear in the proceedings of the TAUP 2011
conference held in Munich (5 - 9 September, 2011
The effect of local optically thick regions in the long-wave emission of young circumstellar disks
Multi-wavelength observations of protoplanetary disks in the sub-millimeter
continuum have measured spectral indices values which are significantly lower
than what is found in the diffuse interstellar medium. Under the assumption
that mm-wave emission of disks is mostly optically thin, these data have been
generally interpreted as evidence for the presence of mm/cm-sized pebbles in
the disk outer regions. In this work we investigate the effect of possible
local optically thick regions on the mm-wave emission of protoplanetary disks
without mm/cm-sized grains. A significant local increase of the optical depth
in the disk can be caused by the concentration of solid particles, as predicted
to result from a variety of proposed physical mechanisms. We calculate the
filling factors and implied overdensities these optically thick regions would
need to significantly affect the millimeter fluxes of disks, and we discuss
their plausibility. We find that optically thick regions characterized by
relatively small filling factors can reproduce the mm-data of young disks
without requesting emission from mm/cm-sized pebbles. However, these optically
thick regions require dust overdensities much larger than what predicted by any
of the physical processes proposed in the literature to drive the concentration
of solids. We find that only for the most massive disks it is possible and
plausible to imagine that the presence of optically thick regions in the disk
is responsible for the low measured values of the mm spectral index. For the
majority of the disk population, optically thin emission from a population of
large mm-sized grains remains the most plausible explanation. The results of
this analysis further strengthen the scenario for which the measured low
spectral indices of protoplanetary disks at mm wavelengths are due to the
presence of large mm/cm-sized pebbles in the disk outer regions.Comment: 13 pages, 2 figures, A&A in pres
Prenatal and Postnatal Nutrition Influence Pancreatic and Intestinal Carbohydrase Activities of Ruminants
In ruminant livestock species, nutrition can play an important role in the long-term programming of gastrointestinal function. Pancreatic and small intestinal digestive enzymes are important for postruminal digestion of carbohydrates and protein. Carbohydrases have been shown to respond to changes in the level of feed intake and the dietary inclusion of specific nutrients, including arginine, butyrate, folic acid, fructose, and leucine. Understanding how diet influences enzyme development and activity during prenatal and postnatal life could lead to the development of dietary strategies to optimize offspring growth and development to increase digestive efficiency of ruminant livestock species. More research is needed to understand how changes in fetal or neonatal carbohydrase activities in response to nutrition influence long-term growth performance and efficiency in ruminant livestock species to optimize nutritional strategies
Highly indistinguishable and strongly entangled photons from symmetric GaAs quantum dots
The development of scalable sources of non-classical light is fundamental to unlocking thetechnological potential of quantum photonics. Semiconductor quantum dots are emerging asnear-optimal sources of indistinguishable single photons. However, their performance assources of entangled-photon pairs are still modest compared to parametric down converters.Photons emitted from conventional StranskiâKrastanov InGaAs quantum dots have shownnon-optimal levels of entanglement and indistinguishability. For quantum networks, bothcriteria must be met simultaneously. Here, we show that this is possible with a system thathas received limited attention so far: GaAs quantum dots. They can emit triggered polar-ization-entangled photons with high purity (g(2)(0) = 0.002±0.002), high indistinguish-ability (0.93±0.07 for 2 ns pulse separation) and high entanglement fidelity(0.94±0.01). Our results show that GaAs might be the material of choice for quantum-dotentanglement sources in future quantum technologie
Measuring the effective complexity of cosmological models
We introduce a statistical measure of the effective model complexity, called
the Bayesian complexity. We demonstrate that the Bayesian complexity can be
used to assess how many effective parameters a set of data can support and that
it is a useful complement to the model likelihood (the evidence) in model
selection questions. We apply this approach to recent measurements of cosmic
microwave background anisotropies combined with the Hubble Space Telescope
measurement of the Hubble parameter. Using mildly non-informative priors, we
show how the 3-year WMAP data improves on the first-year data by being able to
measure both the spectral index and the reionization epoch at the same time. We
also find that a non-zero curvature is strongly disfavored. We conclude that
although current data could constrain at least seven effective parameters, only
six of them are required in a scheme based on the Lambda-CDM concordance
cosmology.Comment: 9 pages, 4 figures, revised version accepted for publication in PRD,
updated with WMAP3 result
Neutrinos and Future Concordance Cosmologies
We review the free parameters in the concordance cosmology, and those which
might be added to this set as the quality of astrophysical data improves. Most
concordance parameters encode information about otherwise unexplored aspects of
high energy physics, up to the GUT scale via the "inflationary sector," and
possibly even the Planck scale in the case of dark energy. We explain how
neutrino properties may be constrained by future astrophysical measurements.
Conversely, future neutrino physics experiments which directly measure these
parameters will remove uncertainty from fits to astrophysical data, and improve
our ability to determine the global properties of our universe.Comment: Proceedings of paper given at Neutrino 2008 meeting (by RE
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