20,914 research outputs found

### Verbal Autopsy Methods with Multiple Causes of Death

Verbal autopsy procedures are widely used for estimating cause-specific
mortality in areas without medical death certification. Data on symptoms
reported by caregivers along with the cause of death are collected from a
medical facility, and the cause-of-death distribution is estimated in the
population where only symptom data are available. Current approaches analyze
only one cause at a time, involve assumptions judged difficult or impossible to
satisfy, and require expensive, time-consuming, or unreliable physician
reviews, expert algorithms, or parametric statistical models. By generalizing
current approaches to analyze multiple causes, we show how most of the
difficult assumptions underlying existing methods can be dropped. These
generalizations also make physician review, expert algorithms and parametric
statistical assumptions unnecessary. With theoretical results, and empirical
analyses in data from China and Tanzania, we illustrate the accuracy of this
approach. While no method of analyzing verbal autopsy data, including the more
computationally intensive approach offered here, can give accurate estimates in
all circumstances, the procedure offered is conceptually simpler, less
expensive, more general, as or more replicable, and easier to use in practice
than existing approaches. We also show how our focus on estimating aggregate
proportions, which are the quantities of primary interest in verbal autopsy
studies, may also greatly reduce the assumptions necessary for, and thus
improve the performance of, many individual classifiers in this and other
areas. As a companion to this paper, we also offer easy-to-use software that
implements the methods discussed herein.Comment: Published in at http://dx.doi.org/10.1214/07-STS247 the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org

### Branching Ratio and Polarization of $B\to\rho(\omega)\rho(\omega)$ Decays in Perturbative QCD Approach

In this work, we calculated the branching ratios, polarization fractions and
CP asymmetry of decay modes $B\to\rho(\omega)\rho(\omega)$ in the Perturbative
QCD approach, which is based on $\mathbf{k}_T$ factorization. After
calculation, we find the the branching ratios of $B^0 \to \rho^+ \rho^-$, $B^+
\to \rho^+ \rho^0$ and $B^+ \to \rho^+ \omega$ are at the order of $10^{-5}$,
and their longitudinal polarization fractions are more than 90%. The above
results agree with BarBar's measurements. We also predict the branching ratios
and polarizations of $B^0 \to \rho^0 \rho^0$, $B^0 \to \rho^0 \omega$ and $B^0
\to \omega \omega$, which will be measured in future. We predicted the CP
asymmetry of $B^0 \to \rho^+ \rho^-$ and $B^+ \to \rho^+ \rho^0$, which will
play important role in determining angle $\alpha$.Comment: 13 pages, 4 figure

### SU(2)-Colored (A)dS Black Holes in Conformal Gravity

We consider four-dimensional conformal gravity coupled to the U(1) Maxwell
and SU(2) Yang-Mills fields. We study the structure of general black hole
solutions carrying five independent parameters: the mass, the electric U(1) and
magnetic SU(2) charges, the massive spin-2 charge and the thermodynamical
pressure associated with the cosmological constant, which is an integration
constant in conformal gravity. We derive the thermodynamical first law of the
black holes. We obtain some exact solutions including an extremal black hole
with vanishing mass and entropy, but with non-trivial SU(2) Yang-Mills charges.
We derive the remainder of the first law for this special solution. We also
reexamine the colored black holes and derive their first law in
Einstein-Yang-Mills gravity with or without a cosmological constant.Comment: Latex, 22 pages, typos corrected and references adde

### Charged Black Holes with Scalar Hair

We consider a class of Einstein-Maxwell-Dilaton theories, in which the
dilaton coupling to the Maxwell field is not the usual single exponential
function, but one with a stationary point. The theories admit two charged black
holes: one is the Reissner-Nordstr{\o}m (RN) black hole and the other has a
varying dilaton. For a given charge, the new black hole in the extremal limit
has the same AdS$_2\times$Sphere near-horizon geometry as the RN black hole,
but it carries larger mass. We then introduce some scalar potentials and obtain
exact charged AdS black holes. We also generalize the results to black
$p$-branes with scalar hair.Comment: Latex, 22 pages, typos corrected and references added, to appear in
JHE

### Spin liquids on a honeycomb lattice: Projective Symmetry Group study of Schwinger fermion mean-field theory

Spin liquids are novel states of matter with fractionalized excitations. A
recent numerical study of Hubbard model on a honeycomb lattice\cite{Meng2010}
indicates that a gapped spin liquid phase exists close to the Mott transition.
Using Projective Symmetry Group, we classify all the possible spin liquid
states by Schwinger fermion mean-field approach. We find there is only one
fully gapped spin liquid candidate state: "Sublattice Pairing State" that can
be realized up to the 3rd neighbor mean-field amplitudes, and is in the
neighborhood of the Mott transition. We propose this state as the spin liquid
phase discovered in the numerical work. To understand whether SPS can be
realized in the Hubbard model, we study the mean-field phase diagram in the
$J_1-J_2$ spin-1/2 model and find an s-wave pairing state. We argue that s-wave
pairing state is not a stable phase and the true ground state may be SPS. A
scenario of a continuous phase transition from SPS to the semimetal phase is
proposed. This work also provides guideline for future variational studies of
Gutzwiller projected wavefunctions.Comment: 13 pages, 4 figures, Revtex

### Charged Black Holes in Colored Lifshitz Spacetimes

We consider Einstein gravities coupled to a cosmological constant and $SU(2)$
Yang-Mills fields in four and five dimensions. We find that the theories admit
colored Lifshitz solutions with dynamic exponents $z>1$. We study the wave
equations of the $SU(2)$ scalar triplet in the bulk, and find that the vacuum
color modifies the scaling dimensions of the dual operators. We also introduce
a Maxwell field and construct exact solutions of electrically-charged black
holes that asymptote to the $D=4$, $z=3$ and $D=5$, $z=4$ colored Lifshitz
spacetimes. We derive the thermodynamical first law for general colored and
charged Lifshitz black holes.Comment: Latex, 13 pages, minor corrections and references adde

### Electrically-Charged Lifshitz Spacetimes, and Hyperscaling Violations

Electrically-charged Lifshitz spacetimes are hard to come by. In this paper,
we construct a class of such solutions in five dimensional Einstein gravity
coupled to Maxwell and $SU(2)$ Yang-Mills fields. The solutions are
electrically-charged under the Maxwell field, whose equation is sourced by the
Yang-Mills instanton(-like) configuration living in the hyperbolic four-space
of the Lifshitz spacetime. We then introduce a dilaton and construct charged
and colored Lifshitz spacetimes with hyperscaling violations. We obtain a class
of exact Lifshitz black holes. We also perform similar constructions in four
dimensions.Comment: Latex, 14 page

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