346 research outputs found
Optimization of Bell's Inequality Violation For Continuous Variable Systems
Two mode squeezed vacuum states allow Bell's inequality violation (BIQV) for
all non-vanishing squeezing parameter . Maximal violation occurs at
when the parity of either component averages to zero. For a
given entangled {\it two spin} system BIQV is optimized via orientations of the
operators entering the Bell operator (cf. S. L. Braunstein, A. Mann and M.
Revzen: Phys. Rev. Lett. {\bf68}, 3259 (1992)). We show that for finite
in continuous variable systems (and in general whenever the dimensionality of
the subsystems is greater than 2) additional parameters are present for
optimizing BIQV. Thus the expectation value of the Bell operator depends, in
addition to the orientation parameters, on configuration parameters.
Optimization of these configurational parameters leads to a unique maximal BIQV
that depends only on The configurational parameter variation is used
to show that BIQV relation to entanglement is, even for pure state, not
monotonic.Comment: An example added; shows that the amount of Bell's inequality
violation as a measure of entanglement is doubtfu
CPT theorem in a (5+1) Galilean space-time
We extend the 5-dimensional Galilean space-time to a (5+1) Galilean
space-time in order to define a parity transformation in a covariant manner.
This allows us to discuss the discrete symmetries in the Galilean space-time,
which is embedded in the (5+1) Minkowski space-time. We discuss the Dirac-type
field, for which we give the 8\times 8 gamma matrices explicitly. We
demonstrate that the CPT theorem holds in the (5+1) Galilean space-time.Comment: 11 pages, 0 figur
New evidence for strong nonthermal effects in Tycho's supernova remnant
For the case of Tycho's supernova remnant (SNR) we present the relation
between the blast wave and contact discontinuity radii calculated within the
nonlinear kinetic theory of cosmic ray (CR) acceleration in SNRs. It is
demonstrated that these radii are confirmed by recently published Chandra
measurements which show that the observed contact discontinuity radius is so
close to the shock radius that it can only be explained by efficient CR
acceleration which in turn makes the medium more compressible. Together with
the recently determined new value erg of the SN
explosion energy this also confirms our previous conclusion that a TeV
gamma-ray flux of erg/(cms) is to be expected from
Tycho's SNR. Chandra measurements and the HEGRA upper limit of the TeV
gamma-ray flux together limit the source distance to kpc.Comment: 5 pages, 4 figures. Accepted for publication in Astrophysics and
Space Science, Proc. of "The Multi-Messenger Approach to High-Energy
Gamma-ray Sources (Third Workshop on the Nature of Unidentified High-Energy
Sources)", Barcelona, July 4-7, 200
Particle Dark Matter Constraints from the Draco Dwarf Galaxy
It is widely thought that neutralinos, the lightest supersymmetric particles,
could comprise most of the dark matter. If so, then dark halos will emit radio
and gamma ray signals initiated by neutralino annihilation. A particularly
promising place to look for these indicators is at the center of the local
group dwarf spheroidal galaxy Draco, and recent measurements of the motion of
its stars have revealed it to be an even better target for dark matter
detection than previously thought. We compute limits on WIMP properties for
various models of Draco's dark matter halo. We find that if the halo is nearly
isothermal, as the new measurements indicate, then current gamma ray flux
limits prohibit much of the neutralino parameter space. If Draco has a moderate
magnetic field, then current radio limits can rule out more of it. These
results are appreciably stronger than other current constraints, and so
acquiring more detailed data on Draco's density profile becomes one of the most
promising avenues for identifying dark matter.Comment: 13 pages, 6 figure
Identifying Residents Who May Benefit from an Analgesic Review: Applying Analgesic Indicators in Residential Aged Care Services.
Background Ensuring safe and effective analgesic use in residential aged care services is important because older adults are susceptible to analgesic-related adverse drug events (ADEs). Objective The aim of this study was to identify the proportion and characteristics of residents of aged care services who may benefit from analgesic review based on indicators in the 2021 Society for Post-Acute and Long-Term Care Medicine (AMDA) Pain Management Guideline. Methods Cross-sectional analyses of baseline data from the Frailty in Residential Sector over Time (FIRST) study (N = 550 residents) across 12 South Australian residential aged care services in 2019 were conducted. Indicators included the proportion of residents who received > 3000 mg/day of acetaminophen (paracetamol), regular opioids without a documented clinical rationale, opioid doses > 60 mg morphine equivalents (MME)/day, more than one long-acting opioid concurrently, and a pro re nata (PRN) opioid on more than two occasions in the previous 7 days. Logistic regression was performed to investigate factors associated with residents who may benefit from analgesic review. Results Of 381 (69.3%) residents charted regular acetaminophen, 176 (46.2%) were charted > 3000 mg/day. Of 165 (30%) residents charted regular opioids, only 2 (1.2%) had no prespecified potentially painful conditions in their medical record and 31 (18.8%) received > 60 MME/day. Of 153 (27.8%) residents charted long-acting opioids, 8 (5.2%) received more than one long-acting opioid concurrently. Of 212 (38.5%) residents charted PRN opioids, 10 (4.7%) received more than two administrations in the previous 7 days. Overall, 196 (35.6%) of 550 residents were identified as potentially benefiting from analgesic review. Females (odds ratio [OR] 1.87, 95% confidence interval [CI] 1.20–2.91) and residents with prior fracture (OR 1.62, 95% CI 1.12–2.33) were more likely to be identified. Observed pain (OR 0.50, 95% CI 0.29–0.88) was associated with a lower likelihood of being identified compared with residents with no observed pain. Overall, 43 (7.8%) residents were identified based on opioid-related indicators. Conclusions Up to one in three residents may benefit from a review of their analgesic regimen, including 1 in 13 who may benefit from a specific review of their opioid regimen. Analgesic indicators represent a new approach to target analgesic stewardship interventions.Laura A. Dowd, Amanda J. Cross, Shin J. Liau, Agathe D. Jadczak, Renuka Visvanathan, Felicity C. Veal, J. Simon Bel
Magnetic Fields, Relativistic Particles, and Shock Waves in Cluster Outskirts
It is only now, with low-frequency radio telescopes, long exposures with
high-resolution X-ray satellites and gamma-ray telescopes, that we are
beginning to learn about the physics in the periphery of galaxy clusters. In
the coming years, Sunyaev-Zeldovich telescopes are going to deliver further
great insights into the plasma physics of these special regions in the
Universe. The last years have already shown tremendous progress with detections
of shocks, estimates of magnetic field strengths and constraints on the
particle acceleration efficiency. X-ray observations have revealed shock fronts
in cluster outskirts which have allowed inferences about the microphysical
structure of shocks fronts in such extreme environments. The best indications
for magnetic fields and relativistic particles in cluster outskirts come from
observations of so-called radio relics, which are megaparsec-sized regions of
radio emission from the edges of galaxy clusters. As these are difficult to
detect due to their low surface brightness, only few of these objects are
known. But they have provided unprecedented evidence for the acceleration of
relativistic particles at shock fronts and the existence of muG strength fields
as far out as the virial radius of clusters. In this review we summarise the
observational and theoretical state of our knowledge of magnetic fields,
relativistic particles and shocks in cluster outskirts.Comment: 34 pages, to be published in Space Science Review
Magnetic fields in cosmic particle acceleration sources
We review here some magnetic phenomena in astrophysical particle accelerators
associated with collisionless shocks in supernova remnants, radio galaxies and
clusters of galaxies. A specific feature is that the accelerated particles can
play an important role in magnetic field evolution in the objects. We discuss a
number of CR-driven, magnetic field amplification processes that are likely to
operate when diffusive shock acceleration (DSA) becomes efficient and
nonlinear. The turbulent magnetic fields produced by these processes determine
the maximum energies of accelerated particles and result in specific features
in the observed photon radiation of the sources. Equally important, magnetic
field amplification by the CR currents and pressure anisotropies may affect the
shocked gas temperatures and compression, both in the shock precursor and in
the downstream flow, if the shock is an efficient CR accelerator. Strong
fluctuations of the magnetic field on scales above the radiation formation
length in the shock vicinity result in intermittent structures observable in
synchrotron emission images. Resonant and non-resonant CR streaming
instabilities in the shock precursor can generate mesoscale magnetic fields
with scale-sizes comparable to supernova remnants and even superbubbles. This
opens the possibility that magnetic fields in the earliest galaxies were
produced by the first generation Population III supernova remnants and by
clustered supernovae in star forming regions.Comment: 30 pages, Space Science Review
Magnetic Reconnection in Extreme Astrophysical Environments
Magnetic reconnection is a basic plasma process of dramatic rearrangement of
magnetic topology, often leading to a violent release of magnetic energy. It is
important in magnetic fusion and in space and solar physics --- areas that have
so far provided the context for most of reconnection research. Importantly,
these environments consist just of electrons and ions and the dissipated energy
always stays with the plasma. In contrast, in this paper I introduce a new
direction of research, motivated by several important problems in high-energy
astrophysics --- reconnection in high energy density (HED) radiative plasmas,
where radiation pressure and radiative cooling become dominant factors in the
pressure and energy balance. I identify the key processes distinguishing HED
reconnection: special-relativistic effects; radiative effects (radiative
cooling, radiation pressure, and Compton resistivity); and, at the most extreme
end, QED effects, including pair creation. I then discuss the main
astrophysical applications --- situations with magnetar-strength fields
(exceeding the quantum critical field of about 4 x 10^13 G): giant SGR flares
and magnetically-powered central engines and jets of GRBs. Here, magnetic
energy density is so high that its dissipation heats the plasma to MeV
temperatures. Electron-positron pairs are then copiously produced, making the
reconnection layer highly collisional and dressing it in a thick pair coat that
traps radiation. The pressure is dominated by radiation and pairs. Yet,
radiation diffusion across the layer may be faster than the global Alfv\'en
transit time; then, radiative cooling governs the thermodynamics and
reconnection becomes a radiative transfer problem, greatly affected by the
ultra-strong magnetic field. This overall picture is very different from our
traditional picture of reconnection and thus represents a new frontier in
reconnection research.Comment: Accepted to Space Science Reviews (special issue on magnetic
reconnection). Article is based on an invited review talk at the
Yosemite-2010 Workshop on Magnetic Reconnection (Yosemite NP, CA, USA;
February 8-12, 2010). 30 pages, no figure
The Fueling and Evolution of AGN: Internal and External Triggers
In this chapter, I review the fueling and evolution of active galactic nuclei
(AGN) under the influence of internal and external triggers, namely intrinsic
properties of host galaxies (morphological or Hubble type, color, presence of
bars and other non-axisymmetric features, etc) and external factors such as
environment and interactions. The most daunting challenge in fueling AGN is
arguably the angular momentum problem as even matter located at a radius of a
few hundred pc must lose more than 99.99 % of its specific angular momentum
before it is fit for consumption by a BH. I review mass accretion rates,
angular momentum requirements, the effectiveness of different fueling
mechanisms, and the growth and mass density of black BHs at different epochs. I
discuss connections between the nuclear and larger-scale properties of AGN,
both locally and at intermediate redshifts, outlining some recent results from
the GEMS and GOODS HST surveys.Comment: Invited Review Chapter to appear in LNP Volume on "AGN Physics on All
Scales", Chapter 6, in press. 40 pages, 12 figures. Typo in Eq 5 correcte
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