32,758 research outputs found
Gravothermal Catastrophe, an Example
This work discusses gravothermal catastrophe in astrophysical systems and
provides an analytic collapse solution which exhibits many of the catastrophe
properties. The system collapses into a trapped surface with outgoing energy
radiated to a future boundary, and provides an example of catastrophic
collapse.Comment: To appear in Phys. Rev.
Partial separability and entanglement criteria for multiqubit quantum states
We explore the subtle relationships between partial separability and
entanglement of subsystems in multiqubit quantum states and give experimentally
accessible conditions that distinguish between various classes and levels of
partial separability in a hierarchical order. These conditions take the form of
bounds on the correlations of locally orthogonal observables. Violations of
such inequalities give strong sufficient criteria for various forms of partial
inseparability and multiqubit entanglement. The strength of these criteria is
illustrated by showing that they are stronger than several other well-known
entanglement criteria (the fidelity criterion, violation of Mermin-type
separability inequalities, the Laskowski-\.Zukowski criterion and the
D\"ur-Cirac criterion), and also by showing their great noise robustness for a
variety of multiqubit states, including N-qubit GHZ states and Dicke states.
Furthermore, for N greater than or equal to 3 they can detect bound entangled
states. For all these states, the required number of measurement settings for
implementation of the entanglement criteria is shown to be only N+1. If one
chooses the familiar Pauli matrices as single-qubit observables, the
inequalities take the form of bounds on the anti-diagonal matrix elements of a
state in terms of its diagonal matrix elements.Comment: 25 pages, 3 figures. v4: published versio
Dispersive approach to the axial anomaly and nonrenormalization theorem
Anomalous triangle graphs for the divergence of the axial-vector current are
studied using the dispersive approach generalized for the case of higher orders
of perturbation theory. The validity of this procedure is proved up to two-loop
level. By direct calculation in the framework of dispersive approach we have
obtained that the two-loop AVV amplitude is equal to zero. According to the
Vainshtein's theorem the transversal part of the anomalous triangle is not
renormalized in the chiral limit. We generalize this theorem for tha case of
finite fermion mass in the triangle loop.Comment: 12 pages, version to appear in Physical Review
Probing protein-protein interactions by dynamic force correlated spectroscopy (FCS)
We develop a formalism for single molecule dynamic force spectroscopy to map
the energy landscape of protein-protein complex (). The joint
distribution of unbinding lifetimes and
measurable in a compression-tension cycle, which accounts for the internal
relaxation dynamics of the proteins under tension, shows that the histogram of
is not Poissonian. The theory is applied to the forced unbinding of
protein , modeled as a wormlike chain, from . We propose a new
class of experiments which can resolve the effect of internal protein dynamics
on the unbinding lifetimes.Comment: 12 pages, 3 figures, accepted to Phys. Rev. Let
Anomalously Weak Dynamical Friction in Halos
A bar rotating in a pressure-supported halo generally loses angular momentum
and slows down due to dynamical friction. Valenzuela & Klypin report a
counter-example of a bar that rotates in a dense halo with little friction for
several Gyr, and argue that their result invalidates the claim by Debattista &
Sellwood that fast bars in real galaxies require a low halo density. We show
that it is possible for friction to cease for a while should the pattern speed
of the bar fluctuate upward. The reduced friction is due to an anomalous
gradient in the phase-space density of particles at the principal resonance
created by the earlier evolution. The result obtained by Valenzuela & Klypin is
probably an artifact of their adaptive mesh refinement method, but anyway could
not persist in a real galaxy. The conclusion by Debattista & Sellwood still
stands.Comment: To appear in "Island Universes - Structure and Evolution of Disk
Galaxies" ed. R. S. de Jong, 8 pages, 4 figures, .cls and .sty files include
Applying Quality Improvement methods to address gaps in medicines reconciliation at transfers of care from an acute UK hospital
© Published by the BMJ Publishing Group Limited.Objectives Reliable reconciliation of medicines at admission and discharge from hospital is key to reducing unintentional prescribing discrepancies at transitions of healthcare. We introduced a team approach to the reconciliation process at an acute hospital with the aim of improving the provision of information and documentation of reliable medication lists to enable clear, timely communications on discharge. Setting An acute 400-bedded teaching hospital in London, UK. Participants The effects of change were measured in a simple random sample of 10 adult patients a week on the acute admissions unit over 18â €...months. Interventions Quality improvement methods were used throughout. Interventions included education and training of staff involved at ward level and in the pharmacy department, introduction of medication documentation templates for electronic prescribing and for communicating information on medicines in discharge summaries co-designed with patient representatives. Results Statistical process control analysis showed reliable documentation (complete, verified and intentional changes clarified) of current medication on 49.2% of patients discharge summaries. This appears to have improved (to 85.2%) according to a poststudy audit the year after the project end. Pharmacist involvement in discharge reconciliation increased significantly, and improvements in the numbers of medicines prescribed in error, or omitted from the discharge prescription, are demonstrated. Variation in weekly measures is seen throughout but particularly at periods of changeover of new doctors and introduction of new systems. Conclusions New processes led to a sustained increase in reconciled medications and, thereby, an improvement in the number of patients discharged from hospital with unintentional discrepancies (errors or omissions) on their discharge prescription. The initiatives were pharmacist-led but involved close working and shared understanding about roles and responsibilities between doctors, nurses, therapists, patients and their carers
EPR before EPR: a 1930 Einstein-Bohr thought experiment revisited
In 1930 Einstein argued against consistency of the time-energy uncertainty
relation by discussing a thought experiment involving a measurement of mass of
the box which emitted a photon. Bohr seemingly triumphed over Einstein by
arguing that the Einstein's own general theory of relativity saves the
consistency of quantum mechanics. We revisit this thought experiment from a
modern point of view at a level suitable for undergraduate readership and find
that neither Einstein nor Bohr was right. Instead, this thought experiment
should be thought of as an early example of a system demonstrating nonlocal
"EPR" quantum correlations, five years before the famous
Einstein-Podolsky-Rosen paper.Comment: 11 pages, revised, accepted for publication in Eur. J. Phy
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The external morphology of the termite Reticulitermes flavipes Kollar (order, Isoptera).
Violation of Bell's inequalities implies distillability for N qubits
We consider quantum systems composed of qubits, and the family of all
Bell's correlation inequalities for two two-valued measurements per site. We
show that if a -qubit state violates any of these inequalities, then
it is at least bipartite distillable. Indeed there exists a link between the
amount of Bell's inequality violation and the degree of distillability. Thus,
we strengthen the interpretation of Bell's inequalities as detectors of useful
entanglement.Comment: 6 pages, 3 figures, REVTEX. List of authors extended. Partially
rewritten, a rather qualitative explanation of the results. Conclusions
unchange
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