20,914 research outputs found

    Verbal Autopsy Methods with Multiple Causes of Death

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    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→ρ(Ο‰)ρ(Ο‰)B\to\rho(\omega)\rho(\omega) Decays in Perturbative QCD Approach

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    In this work, we calculated the branching ratios, polarization fractions and CP asymmetry of decay modes B→ρ(Ο‰)ρ(Ο‰)B\to\rho(\omega)\rho(\omega) in the Perturbative QCD approach, which is based on kT\mathbf{k}_T factorization. After calculation, we find the the branching ratios of B0→ρ+Οβˆ’B^0 \to \rho^+ \rho^-, B+→ρ+ρ0B^+ \to \rho^+ \rho^0 and B+→ρ+Ο‰B^+ \to \rho^+ \omega are at the order of 10βˆ’510^{-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 B0→ρ0ρ0B^0 \to \rho^0 \rho^0, B0→ρ0Ο‰B^0 \to \rho^0 \omega and B0→ωωB^0 \to \omega \omega, which will be measured in future. We predicted the CP asymmetry of B0→ρ+Οβˆ’B^0 \to \rho^+ \rho^- and B+→ρ+ρ0B^+ \to \rho^+ \rho^0, which will play important role in determining angle Ξ±\alpha.Comment: 13 pages, 4 figure

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

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    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

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    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 AdS2Γ—_2\timesSphere 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 pp-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

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    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 J1βˆ’J2J_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

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    We consider Einstein gravities coupled to a cosmological constant and SU(2)SU(2) Yang-Mills fields in four and five dimensions. We find that the theories admit colored Lifshitz solutions with dynamic exponents z>1z>1. We study the wave equations of the SU(2)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=4D=4, z=3z=3 and D=5D=5, z=4z=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

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    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)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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