517 research outputs found
Corrections to the Nuclear Axial Vector Coupling in a Nuclear Medium
We examine further corrections to the time component of the axial vector
coupling constant in a nuclear medium. The dominant correction is that of
exchange currents. The corrections we examine make the remaining discrepancy
worse.Comment: 6 pages, 2 figure
Scaling Of Chiral Lagrangians And Landau Fermi Liquid Theory For Dense Hadronic Matter
We discuss the Fermi-liquid properties of hadronic matter derived from a
chiral Lagrangian field theory in which Brown-Rho (BR) scaling is incorporated.
We identify the BR scaling as a contribution to Landau's Fermi liquid
fixed-point quasiparticle parameter from "heavy" isoscalar meson degrees of
freedom that are integrated out from a low-energy effective Lagrangian. We show
that for the vector (convection) current, the result obtained in the chiral
Lagrangian approach agrees precisely with that obtained in the
semi-phenomenological Landau-Migdal approach. This precise agreement allows one
to determine the Landau parameter that enters in the effective nucleon mass in
terms of the constant that characterizes BR scaling. When applied to the weak
axial current, however, these two approaches differ in a subtle way. While the
difference is small numerically, the chiral Lagrangian approach implements
current algebra and low-energy theorems associated with the axial response that
the Landau method misses and hence is expected to be more predictive.Comment: 39 pages, latex with 4 eps figure, modified addresses and reference
Long-Time Asymptotics for Solutions of the NLS Equation with a Delta Potential and Even Initial Data
We consider the one-dimensional focusing nonlinear Schr\"odinger equation
(NLS) with a delta potential and even initial data. The problem is equivalent
to the solution of the initial/boundary problem for NLS on a half-line with
Robin boundary conditions at the origin. We follow the method of Bikbaev and
Tarasov which utilizes a B\"acklund transformation to extend the solution on
the half-line to a solution of the NLS equation on the whole line. We study the
asymptotic stability of the stationary 1-soliton solution of the equation under
perturbation by applying the nonlinear steepest-descent method for
Riemann-Hilbert problems introduced by Deift and Zhou. Our work strengthens,
and extends, earlier work on the problem by Holmer and Zworski
A comment on -branes of () string theory
We argue that in ()d string theory the existence of NS-NS type -brane
with negative tension is essential to obtain background geometry or on the transverse dimensions, and the usual codimension-2 brane
solutions with these background geometries already contain the negative tension
NS-brane implicity in their ansatz. Such an argument leads us, in the context
of brane world scenarios, to a conjecture that true background -brane
immanent in our spacetime may perhaps be NS-NS type brane, rather than D-brane.Comment: 16 pages. Version to appear in JHE
Supersymmetric Intersections of M-branes and pp-waves
We study supersymmetric intersections of M2 and M5 branes with different
pp-waves of M-theory. We consider first M-brane probes in the background of
pp-waves and determine under which conditions the embedding is supersymmetric.
We particularize our formalism to the case of pp-waves with 32, 24 and 20
supersymmetries. We also construct supergravity solutions for the brane-wave
system. Generically these solutions are delocalised along some directions
transverse to the brane and preserve the same number of supersymmetries as in
the brane probe approach.Comment: 41 pages, LaTeX; v2 references adde
Open Spinning Strings and AdS/dCFT Duality
We consider open spinning string solutions on an AdS_4 x S^2-brane (D5-brane)
in the bulk AdS_5 x S^5 background. By taking account of the breaking of
SO(6)_R to SO(3)_H x SO(3)_V due to the presence of the AdS-brane, the open
rotating string ansatz is discussed. We construct the elliptic folded/circular
open string solutions in the SU(2) and the SL(2) sectors, so that they satisfy
the appropriate boundary conditions. On the other hand, in the SU(2) sector of
the gauge theory, we compute the matrix of anomalous dimension of the defect
operator, which turns out to be the Hamiltonian of an open integrable spin
chain. Then we consider the coordinate Bethe ansatz with arbitrary number of
impurities, and compare the boundary condition of the Bethe wavefunction with
that of the corresponding open string solution. We also discuss the Bethe
ansatz for the open SL(2) spin chain with several supports from the string
theory side. Then, in both SU(2) and SL(2) sectors, we analyze the Bethe
equations in the thermodynamic limit and formulate the `doubling trick' on the
Riemann surface associated with the gauge theory.Comment: 1+50 pages, 7 figures, JHEP style, references adde
The COSINE-100 liquid scintillator veto system
This paper describes the liquid scintillator veto system for the COSINE-100 dark matter experiment and its performance. The COSINE-100 detector consists of eight NaI(Tl) crystals immersed in 2200 L of linear alkylbenzene-based liquid scintillator. The liquid scintillator tags between 65 and 75% of the internal 40K background in the 2–6 keV energy region. We also describe the background model for the liquid scintillator, which is primarily used to assess its energy calibration and threshold
Measurement of the cosmic muon annual and diurnal flux variation with the COSINE-100 detector
We report measurements of annual and diurnal modulations of the cosmic-ray muon rate in the Yangyang underground laboratory (Y2L) using 952 days of COSINE-100 data acquired between September 2016 and July 2019. A correlation of the muon rate with the atmospheric temperature is observed and its amplitude on the muon rate is determined. The effective atmospheric temperature and muon rate variations are positively correlated with a measured effective temperature coefficient of αT = 0.80 ± 0.11. This result is consistent with a model of meson production in the atmosphere. We also searched for a diurnal modulation in the underground muon rate by comparing one-hour intervals. No significant diurnal modulation of the muon rate was observed
Towards actionable international comparisons of health system performance: expert revision of the OECD framework and quality indicators
Objective To review and update the conceptual framework, indicator content and research priorities of the Organisation for Economic Cooperation and Development's (OECD) Health Care Quality Indicators (HCQI) project, after a decade of collaborative work. Design A structured assessment was carried out using a modified Delphi approach, followed by a consensus meeting, to assess the suite of HCQI for international comparisons, agree on revisions to the original framework and set priorities for research and development. Setting International group of countries participating to OECD projects. Participants Members of the OECD HCQI expert group. Results A reference matrix, based on a revised performance framework, was used to map and assess all seventy HCQI routinely calculated by the OECD expert group. A total of 21 indicators were agreed to be excluded, due to the following concerns: (i) relevance, (ii) international comparability, particularly where heterogeneous coding practices might induce bias, (iii) feasibility, when the number of countries able to report was limited and the added value did not justify sustained effort and (iv) actionability, for indicators that were unlikely to improve on the basis of targeted policy interventions. Conclusions The revised OECD framework for HCQI represents a new milestone of a long-standing international collaboration among a group of countries committed to building common ground for performance measurement. The expert group believes that the continuation of this work is paramount to provide decision makers with a validated toolbox to directly act on quality improvement strategie
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