2,313 research outputs found
Minimally Allowed Neutrinoless Double Beta Decay Rates From Approximate Flavor Symmetries
Neutrinoless double beta decay () is among the only realistic
probes of Majorana neutrinos. In the standard scenario, dominated by light
neutrino exchange, the process amplitude is proportional to , the
element of the Majorana mass matrix. Naively, current data allows for vanishing
, but this should be protected by an appropriate flavor symmetry. All
such symmetries lead to mass matrices inconsistent with oscillation
phenomenology. I perform a spurion analysis to break all possible Abelian
symmetries that guarantee vanishing rates and search for
minimally allowed values. I survey 230 broken structures to yield
values and current phenomenological constraints under a variety of scenarios.
This analysis also extracts predictions for both neutrino oscillation
parameters and kinematic quantities. Assuming reasonable tuning levels, I find
that eV at 99% confidence. Bounds below this value
might indicate the Dirac neutrino nature or the existence of new light (eV-MeV
scale) degrees of freedom that can potentially be probed elsewhere.Comment: 19 Pages, 4 .eps Figures, 3 Table
Minimally Allowed Neutrinoless Double Beta Decay Rates Within an Anarchical Framework
Neutrinoless double beta decay is the only realistic probe of the Majorana
nature of the neutrino. In the standard picture, its rate is proportional to
, the e-e element of the Majorana neutrino mass matrix in the flavor
basis. I explore minimally allowed values within the framework of mass
matrix anarchy where neutrino parameters are defined statistically at low
energies. Distributions of mixing angles are well defined by the Haar
integration measure, but masses are dependent on arbitrary weighting functions
and boundary conditions. I survey the integration measure parameter space and
find that for sufficiently convergent weightings, is constrained
between (0.01-0.4) eV at 90% confidence. Constraints from neutrino mixing data
lower these bounds. Singular integration measures allow for arbitrarily small
values with the remaining elements ill-defined, but this condition
constrains the flavor structure of the model's ultraviolet completion. Bounds
below eV should indicate symmetry in the lepton
sector, new light degrees of freedom or the Dirac nature of the neutrino.Comment: BibTeX, 7 pages, 1 .eps Figure, Modified to match content of
published paper: References added, table added, clarified discussion. Results
are unchange
Factors Influencing Selection of Information Sources by Cotton Producers Considering Adoption of Precision Agriculture Technologies
Acknowledgements: The authors thank Cotton Incorporated and the Tennessee Agricultural Experiment Station for financial supportInformation source use decisions, Precision Agriculture Technologies, Extension, Media, Private sources, Multivariate Probit, Teaching/Communication/Extension/Profession, Q12, Q16,
Factors Influencing the Selection of Precision Farming Information Sources by Cotton Producers
Precision farming information demanded by cotton producers is provided by various suppliers, including consultants, farm input dealerships, University Extension systems, and media sources. Factors associated with the decisions to select among information sources to search for precision farming information are analyzed using a multivariate probit regression accounting for correlation among the different selection decisions. Factors influencing these decisions are age, education, and income. These findings should be valuable to precision farming information providers who may be able to better meet their target clientele needs.Extension, information-source-use decisions, media, multivariate probit, precision agriculture technologies, private sources, Farm Management, Teaching/Communication/Extension/Profession,
Economics of Field Pea Supplementation for Cattle Grazing Crested Wheatgrass
Heifers grazing crested wheat grass were supplemented either field peas or dried distillers grains plus solubles (DDGS) at 0.4% or 0.8% of body weight. Heifers supplemented with field peas had 10% lower daily gain compared to their DDGS supplemented counterparts. The decision to supplement field peas for producers depends on the price at which field peas can be acquired, as well as the distance that DDGS has to be hauled in order to be utilized. Field peas are a viable option in western Nebraska as a supplement for grazing cattle when DDGS is unavailable or field peas are in excess and can be obtained below the human consumption and pet food market price
The test case of HD26965: difficulties disentangling weak Doppler signals from stellar activity
We report the discovery of a radial velocity signal that can be interpreted
as a planetary-mass candidate orbiting the K dwarf HD26965, with an orbital
period of 42.3640.015 days, or alternatively, as the presence of residual,
uncorrected rotational activity in the data. Observations include data from
HIRES, PFS, CHIRON, and HARPS, where 1,111 measurements were made over 16
years. Our best solution for HD26965 is consistent with a super-Earth that
has a minimum mass of 6.920.79 M orbiting at a distance of
0.2150.008 AU from its host star. We have analyzed the correlation between
spectral activity indicators and the radial velocities from each instrument,
showing moderate correlations that we include in our model. From this analysis,
we recover a 38 day signal, which matches some literature values of the
stellar rotation period. However, from independent Mt. Wilson HK data for this
star, we find evidence for a significant 42 day signal after subtraction of
longer period magnetic cycles, casting doubt on the planetary hypothesis for
this period. Although our statistical model strongly suggests that the 42-day
signal is Doppler in origin, we conclude that the residual effects of stellar
rotation are difficult to fully model and remove from this dataset,
highlighting the difficulties to disentangle small planetary signals and
photospheric noise, particularly when the orbital periods are close to the
rotation period of the star. This study serves as an excellent test case for
future works that aim to detect small planets orbiting `Sun-like' stars using
radial velocity measurements.Comment: 16 pages, 10 figures, 13 tables, accepted for publication in A
Inherent Rheology of a Granular Fluid in Uniform Shear Flow
In contrast to normal fluids, a granular fluid under shear supports a steady
state with uniform temperature and density since the collisional cooling can
compensate locally for viscous heating. It is shown that the hydrodynamic
description of this steady state is inherently non-Newtonian. As a consequence,
the Newtonian shear viscosity cannot be determined from experiments or
simulation of uniform shear flow. For a given degree of inelasticity, the
complete nonlinear dependence of the shear viscosity on the shear rate requires
the analysis of the unsteady hydrodynamic behavior. The relationship to the
Chapman-Enskog method to derive hydrodynamics is clarified using an approximate
Grad's solution of the Boltzmann kinetic equationComment: 10 pages, 4 figures; substantially enlarged version; to be published
in PR
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Eating disorders, perfectionism and quality of life: Maladaptive perfectionism as a mediator between symptoms of disordered eating and quality of life
Individuals with disordered eating behaviours exhibit significantly impaired quality of life (QoL). Maladaptive perfectionism is consistently associated with both eating disorders (EDs) and QoL, but its role in the relationship between eating pathology and QoL has remained largely unexplored. The current study investigated whether maladaptive perfectionism mediates the ED–QoL relationship. 286 university students completed an online survey which consisted of self-report questionnaires assessing ED symptomology, QoL, maladaptive perfectionism, and anxiety and depression symptoms. Maladaptive perfectionism mediated the relationship between ED symptomology and QoL, but this effect did not persist when body mass index, depression, and anxiety were controlled for. The results suggest the mediatory effect of maladaptive perfectionism is masked by depression and anxiety symptomology. Recommendations for further research are proposed to clarify the role of maladaptive perfectionism in the ED–QoL relationship, and to explore the mediatory role of depression and anxiety in this relationship
Long-lived space observatories for astronomy and astrophysics
NASA's plan to build and launch a fleet of long-lived space observatories that include the Hubble Space Telescope (HST), the Gamma Ray Observatory (GRO), the Advanced X Ray Astrophysics Observatory (AXAF), and the Space Infrared Telescope Facility (SIRTF) are discussed. These facilities are expected to have a profound impact on the sciences of astronomy and astrophysics. The long-lived observatories will provide new insights about astronomical and astrophysical problems that range from the presence of planets orbiting nearby stars to the large-scale distribution and evolution of matter in the universe. An important concern to NASA and the scientific community is the operation and maintenance cost of the four observatories described above. The HST cost about 160 million (1986 dollars) a year to operate and maintain. If HST is operated for 20 years, the accumulated costs will be considerably more than those required for its construction. Therefore, it is essential to plan carefully for observatory operations and maintenance before a long-lived facility is constructed. The primary goal of this report is to help NASA develop guidelines for the operations and management of these future observatories so as to achieve the best possible scientific results for the resources available. Eight recommendations are given
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