750 research outputs found
Cosmological quantum entanglement
We review recent literature on the connection between quantum entanglement
and cosmology, with an emphasis on the context of expanding universes. We
discuss recent theoretical results reporting on the production of entanglement
in quantum fields due to the expansion of the underlying spacetime. We explore
how these results are affected by the statistics of the field (bosonic or
fermionic), the type of expansion (de Sitter or asymptotically stationary), and
the coupling to spacetime curvature (conformal or minimal). We then consider
the extraction of entanglement from a quantum field by coupling to local
detectors and how this procedure can be used to distinguish curvature from
heating by their entanglement signature. We review the role played by quantum
fluctuations in the early universe in nucleating the formation of galaxies and
other cosmic structures through their conversion into classical density
anisotropies during and after inflation. We report on current literature
attempting to account for this transition in a rigorous way and discuss the
importance of entanglement and decoherence in this process. We conclude with
some prospects for further theoretical and experimental research in this area.
These include extensions of current theoretical efforts, possible future
observational pursuits, and experimental analogues that emulate these cosmic
effects in a laboratory setting.Comment: 23 pages, 2 figures. v2 Added journal reference and minor changes to
match the published versio
Electrostatic boundary value problems in the Schwarzschild background
The electrostatic potential of any test charge distribution in Schwarzschild
space with boundary values is derived. We calculate the Green's function,
generalize the second Green's identity for p-forms and find the general
solution. Boundary value problems are solved. With a multipole expansion the
asymptotic property for the field of any charge distribution is derived. It is
shown that one produces a Reissner--Nordstrom black hole if one lowers a test
charge distribution slowly toward the horizon. The symmetry of the distribution
is not important. All the multipole moments fade away except the monopole. A
calculation of the gravitationally induced electrostatic self-force on a
pointlike test charge distribution held stationary outside the black hole is
presented.Comment: 18 pages, no figures, uses iopart.st
Patient engagement with antibiotic messaging in secondary care: a qualitative feasibility study of the ‘review & revise’ experience
Background: We aimed to investigate and optimise the acceptability and usefulness of a patient leaflet about antibiotic prescribing decisions made during hospitalisation, and to explore individual patient experiences and preferences regarding the process of antibiotic prescription ‘review & revise’ which is a key strategy to minimise antibiotic overuse in hospitals.
Methods: In this qualitative study, run within the feasibility study of a large, cluster-randomised stepped wedge trial of 36 hospital organisations, a series of semi-structured, think-aloud telephone interviews were conducted and data were analysed using thematic analysis. Fifteen adult patients who had experienced a recent acute medical hospital admission during which they had been prescribed antimicrobials and offered a patient leaflet about antibiotic prescribing were recruited to the study.
Results: Participants reacted positively to the leaflet, reporting that it was both an accessible and important source of information which struck the appropriate balance between informing and reassuring. Participants all valued open communication with clinicians, and were keen to be involved in antibiotic prescribing decisions, with individuals reporting positive experiences regarding antibiotic prescription changes or stopping. Many participants had prior experience or knowledge of antibiotics and resistance, and generally welcomed efforts to reduce antibiotic usage. Overall, there was a feeling that healthcare professionals (HCPs) are trusted experts providing the most appropriate treatment for individual patient conditions.
Conclusions: This study offers novel insights into how patients within secondary care are likely to respond to messages advocating a reduction in the use of antibiotics through the ‘review & revise’ approach. Due to the level of trust that patients place in their care provider, encouraging HCPs within secondary care to engage patients with greater communication and information provision could provide great advantages in the drive to reduce antibiotic use. It may also be beneficial for HCPs to view patient experiences as cumulative events that have the potential to impact future behaviour around antibiotic use. Finally, pre-testing messages about antibiotic prescribing and resistance is vital to dispelling any misconceptions either around effectiveness of treatment for patients, or perceptions of how messages may be received
Electron Capture Strength for {60,62}Ni and {58,60,62,64}Ni(p,n){58,60,62,64}Cu reactions at 134.3 MeV
Background: The strength of electron capture for medium mass nuclei has a
significant effect on the evolution of supernovae. There is insufficient
knowledge of these strengths and very little data for important radioactive
nuclei. Purpose: Determine whether it is feasible to obtain EC strength from
studies of T_o+1 excitations in (p,n) reactions, and whether this might yield
information for radioactive nuclei. Methods: Cross sections for the
{58,60,62,64}Ni(p,n){58,60,62,64}Cu reactions were measured over the angular
range of 0.3 deg to 11.6 deg at 134.3 MeV using the IUCF neutron time-of-flight
facility. esults: The T_o+1 excitations in {60,62}Ni were identified by
comparison with inelastic proton scattering spectra, their B(GT) were
extracted, and the corresponding electron capture rates in supernovae were
calculated. Data from the TRIUMF (n,p) experiments at 198 MeV were reanalyzed;
the electron capture rates for the reanalyzed data are in moderately good
agreement with the higher resolution (p,n) results, but differ in detail. The
possibility of future measurements with radioactive nuclei was considered.
Conclusions: It is possible to determine electron capturestrength from (p,n)
experiments. This approach may make it possible to obtain electron capture
strength for radioactive nuclei by studying (p,n) reactions in inverse
kinematics.Comment: Submitted to Physical Review
Theorems on shear-free perfect fluids with their Newtonian analogues
In this paper we provide fully covariant proofs of some theorems on
shear-free perfect fluids. In particular, we explicitly show that any
shear-free perfect fluid with the acceleration proportional to the vorticity
vector (including the simpler case of vanishing acceleration) must be either
non-expanding or non-rotating. We also show that these results are not
necessarily true in the Newtonian case, and present an explicit comparison of
shear-free dust in Newtonian and relativistic theories in order to see where
and why the differences appear.Comment: 23 pages, LaTeX. Submitted to GR
Nuclear Transparency to Intermediate-Energy Protons
Nuclear transparency in the (e,e'p) reaction for 135 < Tp < 800 MeV is
investigated using the distorted wave approximation. Calculations using
density-dependent effective interactions are compared with phenomenological
optical potentials. Nuclear transparency is well correlated with proton
absorption and neutron total cross sections. For Tp < 300 MeV there is
considerable sensitivity to the choice of optical model, with the empirical
effective interaction providing the best agreement with transparency data. For
Tp > 300 MeV there is much less difference between optical models, but the
calculations substantially underpredict transparency data and the discrepancy
increases with A. The differences between Glauber and optical model
calculations are related to their respective definitions of the semi-inclusive
cross section. By using a more inclusive summation over final states the
Glauber model emphasizes nucleon-nucleon inelasticity, whereas with a more
restrictive summation the optical model emphasizes nucleon-nucleus
inelasticity; experimental definitions of the semi-inclusive cross section lie
between these extremes.Comment: uuencoded gz-compressed tar file containing revtex and bbl files and
5 postscript figures, totalling 31 pages. Uses psfi
Classification of bicovariant differential calculi on the Jordanian quantum groups GL_{g,h}(2) and SL_{h}(2) and quantum Lie algebras
We classify all 4-dimensional first order bicovariant calculi on the
Jordanian quantum group GL_{h,g}(2) and all 3-dimensional first order
bicovariant calculi on the Jordanian quantum group SL_{h}(2). In both cases we
assume that the bicovariant bimodules are generated as left modules by the
differentials of the quantum group generators. It is found that there are 3
1-parameter families of 4-dimensional bicovariant first order calculi on
GL_{h,g}(2) and that there is a single, unique, 3-dimensional bicovariant
calculus on SL_{h}(2). This 3-dimensional calculus may be obtained through a
classical-like reduction from any one of the three families of 4-dimensional
calculi on GL_{h,g}(2). Details of the higher order calculi and also the
quantum Lie algebras are presented for all calculi. The quantum Lie algebra
obtained from the bicovariant calculus on SL_{h}(2) is shown to be isomorphic
to the quantum Lie algebra we obtain as an ad-submodule within the Jordanian
universal enveloping algebra U_{h}(sl(2)) and also through a consideration of
the decomposition of the tensor product of two copies of the deformed adjoint
module. We also obtain the quantum Killing form for this quantum Lie algebra.Comment: 33 pages, AMSLaTeX, misleading remark remove
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