27,364 research outputs found
New Light Species and the CMB
We consider the effects of new light species on the Cosmic Microwave
Background. In the massless limit, these effects can be parameterized in terms
of a single number, the relativistic degrees of freedom. We perform a thorough
survey of natural, minimal models containing new light species and numerically
calculate the precise contribution of each of these models to this number in
the framework of effective field theory. After reviewing the relevant details
of early universe thermodynamics, we provide a map between the parameters of
any particular theory and the predicted effective number of degrees of freedom.
We then use this map to interpret the recent results from the Cosmic Microwave
Background survey done by the Planck satellite. Using this data, we present new
constraints on the parameter space of several models containing new light
species. Future measurements of the Cosmic Microwave Background can be used
with this map to further constrain the parameter space of all such models.Comment: 38 pages plus appendices and references; 10 figures and 1 table;
references added, discussion of anapole moments added; supernovae cooling
bounds added, discussion of models condense
Protecting unparticles from the MSSM Higgs sector
We construct a model of an unparticle sector consisting of a supersymmetric
SU(N) gauge theory with the number of flavors in the Seiberg conformal window.
We couple this sector to the MSSM via heavy messengers. The resulting low
energy theory has a Higgs coupling to unparticles. The Higgs vev drives the
hidden Seiberg sector to a new conformal fixed point. The coupling to the Higgs
mediates supersymmetry breaking to the Seiberg sector, and breaks conformal
invariance at a lower scale. The low energy theory contains light stable and
metastable mesons. Higgs decay into this sector gives signatures which are
similar to those of "hidden valley" models. Decays of the lightest superpartner
of standard model particles into the hidden sector reveal potentially
observable unparticle kinematics.Comment: References added. 11 pages, 4 figure
Identifying Gaps and Setting Priorities for Employment and Training Research
The report summarizes recent workforce and employment related research, to identify current gaps in employment and training research and makes recommendations for future research processes and priorities that could better inform policy makers, practitioners, job seekers and employers. The report reviews workforce and related research funded by several federal agencies, including the US Departments of Labor, Education, Agriculture, Health and Human Services, and Housing and Urban Development, the National Science Foundation and other federal entities, as well as research undertaken by regional, state and local workforce agencies and philanthrophic organizations
What is Causing This Man\u27s Rectal Pain and Urinary Retention?
Case: A 23-year-old man presented to an urgent care office with a 2-week history of rectal pain and scant rectal bleeding. In the few days leading up to his presentation, he also had a fever of 101° F (38.3° C), inguinal lymphadenopathy, and urinary retention
Money stock control and its implications for monetary policy
Monetary policy ; Money supply
Experimental Verification of Cavity-Flow Wall Effects and Correction Rules
This report is intended as a companion to Report No. E-111A.5, "Wall Efects in Cavity Flows", by Wu, Whitney and Lin. Some simple rules for the correction of wall effect are derived from that theoretical study. Experiments designed to complement the theory and to inspect the validity of the correction rules were then carried out in the high-speed water tunnel of the Hydrodynamics Laboratory, California Institute of Technology. The measurements on a series of fully cavitating wedges at zero angle of attack suggested that of the theoretical models that due to Riabouchinsky is superior. They also confirmed the accuracy of the correction rule derived using that model and based on a measurement of the minimum pressure along the tunnel wall
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Improved V I Log(gf) Values and Abundance Determinations in the Photospheres of the Sun and Metal-Poor Star HD 84937
New emission branching fraction measurements for 836 lines of the first spectrum of vanadium (V I) are determined from hollow cathode lamp spectra recorded with the National Solar Observatory 1 m Fourier transform spectrometer (FTS) and a high-resolution echelle spectrometer. The branching fractions are combined with recently published radiative lifetimes from laser-induced fluorescence measurements to determine accurate absolute atomic transition probabilities for the 836 lines. The FTS data are also used to extract new hyperfine structure A coefficients for 26 levels of neutral vanadium. These new laboratory data are applied to determine the V abundance in the Sun and metal-poor star HD 84937, yielding log epsilon(V) = 3.956 +/- 0.004 (sigma = 0.037) based on 93 V I lines and log epsilon(V) = 1.89 +/- 0.03 (sigma = 0.07) based on nine Vi lines, respectively, using the Holweger-Muller 1D model. These new V I abundance values for the Sun and HD 84937 agree well with our earlier determinations based upon V II.NASA NNX10AN93GNSF AST-1211055, AST-1211585Astronom
Five-Dimensional Unification of the Cosmological Constant and the Photon Mass
Using a non-Riemannian geometry that is adapted to the 4+1 decomposition of
space-time in Kaluza-Klein theory, the translational part of the connection
form is related to the electromagnetic vector potential and a Stueckelberg
scalar. The consideration of a five-dimensional gravitational action functional
that shares the symmetries of the chosen geometry leads to a unification of the
four-dimensional cosmological term and a mass term for the vector potential.Comment: 8 pages, LaTe
Local u'g'r'i'z' Standard Stars in the Chandra Deep Field-South
Because several observing programs are underway in various spectral regimes
to explore the Chandra Deep Field South (CDF-S), the value of local photometric
standards is obvious. As part of an NOAO Surveys Program to establish
u'g'r'i'z' standard stars in the southern hemisphere, we have observed the
central region of the CDF-S to create local standards for use by other
investigators using these filters. As a courtesy, we present the CDF-S
standards to the public now, although the main program will not finish until
mid-2005.Comment: Accepted by AJ (scheduled for October 2003 issue). 26 pages, 5
tables, 5 figures. High resolution version of Figure 7 available at
http://home.fnal.gov/~dtucker/Southern_ugriz/index.htm
A Limited Habitable Zone for Complex Life
The habitable zone (HZ) is commonly defined as the range of distances from a
host star within which liquid water, a key requirement for life, may exist on a
planet's surface. Substantially more CO2 than present in Earth's modern
atmosphere is required to maintain clement temperatures for most of the HZ,
with several bars required at the outer edge. However, most complex aerobic
life on Earth is limited by CO2 concentrations of just fractions of a bar. At
the same time, most exoplanets in the traditional HZ reside in proximity to M
dwarfs, which are more numerous than Sun-like G dwarfs but are predicted to
promote greater abundances of gases that can be toxic in the atmospheres of
orbiting planets, such as carbon monoxide (CO). Here we show that the HZ for
complex aerobic life is likely limited relative to that for microbial life. We
use a 1D radiative-convective climate and photochemical models to circumscribe
a Habitable Zone for Complex Life (HZCL) based on known toxicity limits for a
range of organisms as a proof of concept. We find that for CO2 tolerances of
0.01, 0.1, and 1 bar, the HZCL is only 21%, 32%, and 50% as wide as the
conventional HZ for a Sun-like star, and that CO concentrations may limit some
complex life throughout the entire HZ of the coolest M dwarfs. These results
cast new light on the likely distribution of complex life in the universe and
have important ramifications for the search for exoplanet biosignatures and
technosignatures.Comment: Revised including additional discussion. Published Gold OA in ApJ. 9
pages, 5 figures, 5 table
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