138 research outputs found
The Self-Accelerating Universe with Vectors in Massive Gravity
We explore the possibility of realising self-accelerated expansion of the
Universe taking into account the vector components of a massive graviton. The
effective action in the decoupling limit contains an infinite number of terms,
once the vector degrees of freedom are included. These can be re-summed in
physically interesting situations, which result in non-polynomial couplings
between the scalar and vector modes. We show there are self-accelerating
background solutions for this effective action, with the possibility of having
a non-trivial profile for the vector fields. We then study fluctuations around
these solutions and show that there is always a ghost, if a background vector
field is present. When the background vector field is switched off, the ghost
can be avoided, at the price of entering into a strong coupling regime, in
which the vector fluctuations have vanishing kinetic terms. Finally we show
that the inclusion of a bare cosmological constant does not change the previous
conclusions and it does not lead to a ghost mode in the absence of a background
vector field.Comment: 23 pages, 2 figure
Cosmic Physics: The High Energy Frontier
Cosmic rays have been observed up to energies times larger than those
of the best particle accelerators. Studies of astrophysical particles (hadrons,
neutrinos and photons) at their highest observed energies have implications for
fundamental physics as well as astrophysics. Thus, the cosmic high energy
frontier is the nexus to new particle physics. This overview discusses recent
advances being made in the physics and astrophysics of cosmic rays and cosmic
gamma-rays at the highest observed energies as well as the related physics and
astrophysics of very high energy cosmic neutrinos. These topics touch on
questions of grand unification, violation of Lorentz invariance, as well as
Planck scale physics and quantum gravity.Comment: Topical Review Paper to be published in the Journal of Physics G, 50
page
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Inflation and Dark Energy from spectroscopy at z > 2
The expansion of the Universe is understood to have accelerated during two
epochs: in its very first moments during a period of Inflation and much more
recently, at z < 1, when Dark Energy is hypothesized to drive cosmic
acceleration. The undiscovered mechanisms behind these two epochs represent
some of the most important open problems in fundamental physics. The large
cosmological volume at 2 < z < 5, together with the ability to efficiently
target high- galaxies with known techniques, enables large gains in the
study of Inflation and Dark Energy. A future spectroscopic survey can test the
Gaussianity of the initial conditions up to a factor of ~50 better than our
current bounds, crossing the crucial theoretical threshold of
of order unity that separates single field and
multi-field models. Simultaneously, it can measure the fraction of Dark Energy
at the percent level up to , thus serving as an unprecedented test of
the standard model and opening up a tremendous discovery space
The relation between the most-massive star and its parental star cluster mass
We present a thorough literature study of the most-massive star, m_max, in
several young star clusters in order to assess whether or not star clusters are
populated from the stellar initial mass function (IMF) by random sampling over
the mass range 0.01 < m < 150 M_sol without being constrained by the cluster
mass, M_ecl. The data reveal a partition of the sample into lowest mass objects
(M_ecl < 10^2 M_sol), moderate mass clusters (10^2 M_sol < M_ecl < 10^3 M_sol)
and rich clusters above 10^3 M_sol. Additionally, there is a plateau of a
constant maximal star mass (m_max ~ 25 M_sol) for clusters with masses between
10^3 M_sol and 4 10^3 M_sol. Statistical tests of this data set reveal that the
hypothesis of random sampling from the IMF between 0.01 and 150 M_sol is highly
unlikely for star clusters more massive than 10^2 M_sol with a probability of p
~ 2 10^-7 for the objects with M_ecl between 10^2 M_sol and 10^3 M_sol and p ~
3 10^-9 for the more massive star clusters. Also, the spread of m_max values at
a given M_ecl is smaller than expected from random sampling. We suggest that
the basic physical process able to explain this dependence of stellar inventory
of a star cluster on its mass may be the interplay between stellar feedback and
the binding energy of the cluster-forming molecular cloud core. Given these
results, it would follow that an integrated galactic initial mass function
(IGIMF) sampled from such clusters would automatically be steeper in comparison
to the IMF within individual star clusters.Comment: 26 pages, 13 figures, 3 tables, accepted for publication in MNRA
3D Correlations in the Lyman- Forest from Early DESI Data
We present the first measurements of Lyman- (Ly) forest
correlations using early data from the Dark Energy Spectroscopic Instrument
(DESI). We measure the auto-correlation of Ly absorption using 88,509
quasars at , and its cross-correlation with quasars using a further
147,899 tracer quasars at . Then, we fit these correlations using
a 13-parameter model based on linear perturbation theory and find that it
provides a good description of the data across a broad range of scales. We
detect the BAO peak with a signal-to-noise ratio of , and show that
our measurements of the auto- and cross-correlations are fully-consistent with
previous measurements by the Extended Baryon Oscillation Spectroscopic Survey
(eBOSS). Even though we only use here a small fraction of the final DESI
dataset, our uncertainties are only a factor of 1.7 larger than those from the
final eBOSS measurement. We validate the existing analysis methods of
Ly correlations in preparation for making a robust measurement of the
BAO scale with the first year of DESI data
The Dark Energy Spectroscopic Instrument: one-dimensional power spectrum from first Ly α forest samples with Fast Fourier Transform
We present the one-dimensional Ly α forest power spectrum measurement using the first data provided by the Dark Energy Spectroscopic Instrument (DESI). The data sample comprises 26 330 quasar spectra, at redshift z > 2.1, contained in the DESI Early Data Release and the first 2 months of the main survey. We employ a Fast Fourier Transform (FFT) estimator and compare the resulting power spectrum to an alternative likelihood-based method in a companion paper. We investigate methodological and instrumental contaminants associated with the new DESI instrument, applying techniques similar to previous Sloan Digital Sky Survey (SDSS) measurements. We use synthetic data based on lognormal approximation to validate and correct our measurement. We compare our resulting power spectrum with previous SDSS and high-resolution measurements. With relatively small number statistics, we successfully perform the FFT measurement, which is already competitive in terms of the scale range. At the end of the DESI survey, we expect a five times larger Ly α forest sample than SDSS, providing an unprecedented precise one-dimensional power spectrum measurement
The Lyman- forest catalog from the Dark Energy Spectroscopic Instrument Early Data Release
We present and validate the catalog of Lyman- forest fluctuations for
3D analyses using the Early Data Release (EDR) from the Dark Energy
Spectroscopic Instrument (DESI) survey. We used 96,317 quasars collected from
DESI Survey Validation (SV) data and the first two months of the main survey
(M2). We present several improvements to the method used to extract the
Lyman- absorption fluctuations performed in previous analyses from the
Sloan Digital Sky Survey (SDSS). In particular, we modify the weighting scheme
and show that it can improve the precision of the correlation function
measurement by more than 20%. This catalog can be downloaded from
https://data.desi.lbl.gov/public/edr/vac/edr/lya/fuji/v0.3 and it will be used
in the near future for the first DESI measurements of the 3D correlations in
the Lyman- forest
G6PD testing in support of treatment and elimination of malaria: recommendations for evaluation of G6PD tests
Malaria elimination will be possible only with serious attempts to address asymptomatic infection and chronic infection by both Plasmodium falciparum and Plasmodium vivax. Currently available drugs that can completely clear a human of P. vivax (known as “radical cure”), and that can reduce transmission of malaria parasites, are those in the 8-aminoquinoline drug family, such as primaquine. Unfortunately, people with glucose-6-phosphate dehydrogenase (G6PD) deficiency risk having severe adverse reactions if exposed to these drugs at certain doses. G6PD deficiency is the most common human enzyme defect, affecting approximately 400 million people worldwide. Scaling up radical cure regimens will require testing for G6PD deficiency, at two levels: 1) the individual level to ensure safe case management, and 2) the population level to understand the risk in the local population to guide Plasmodium vivax treatment policy. Several technical and operational knowledge gaps must be addressed to expand access to G6PD deficiency testing and to ensure that a patient’s G6PD status is known before deciding to administer an 8-aminoquinoline-based drug.
In this report from a stakeholder meeting held in Thailand on October 4 and 5, 2012, G6PD testing in support of radical cure is discussed in detail. The focus is on challenges to the development and evaluation of G6PD diagnostic tests, and on challenges related to the operational aspects of implementing G6PD testing in support of radical cure. The report also describes recommendations for evaluation of diagnostic tests for G6PD deficiency in support of radical cure
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