47,767 research outputs found
Additive Entropies of degree-q and the Tsallis Entropy
The Tsallis entropy is shown to be an additive entropy of degree-q that
information scientists have been using for almost forty years. Neither is it a
unique solution to the nonadditive functional equation from which random
entropies are derived. Notions of additivity, extensivity and homogeneity are
clarified. The relation between mean code lengths in coding theory and various
expressions for average entropies is discussed.Comment: 13 page
SINFONI's take on Star Formation, Molecular Gas, and Black Hole Masses in AGN
We present some preliminary (half-way) results on our adaptive optics
spectroscopic survey of AGN at spatial scales down to 0.085arcsec. Most of the
data were obtained with SINFONI which provides integral field capability at a
spectral resolution of R~4000. The themes on which we focus in this
contribution are: star formation around the AGN, the properties of the
molecular gas and its relation to the torus, and the mass of the black hole.Comment: 5 pages, 2 figures. To appear in Science Perspectives for 3D
Spectroscopy. ESO Astrophysics Symposia. Ed by M. Kissler-Patig, M. Roth and
J. Wals
The effects of external planets on inner systems: multiplicities, inclinations, and pathways to eccentric warm Jupiters
We study how close-in systems such as those detected by Kepler are affected
by the dynamics of bodies in the outer system. We consider two scenarios: outer
systems of giant planets potentially unstable to planet--planet scattering, and
wide binaries that may be capable of driving Kozai or other secular variations
of outer planets' eccentricities. Dynamical excitation of planets in the outer
system reduces the multiplicity of Kepler-detectable planets in the inner
system in of our systems. Accounting for the occurrence rates of
wide-orbit planets and binary stars, of close-in systems could be
destabilised by their outer companions in this way. This provides some
contribution to the apparent excess of systems with a single transiting planet
compared to multiple, however, it only contributes at most of the
excess. The effects of the outer dynamics can generate systems similar to
Kepler-56 (two coplanar planets significantly misaligned with the host star)
and Kepler-108 (two significantly non-coplanar planets in a binary). We also
identify three pathways to the formation of eccentric warm Jupiters resulting
from the interaction between outer and inner systems: direct inelastic
collision between an eccentric outer and an inner planet, secular eccentricity
oscillations that may "freeze out" when scattering resolves in the outer
system; and scattering in the inner system followed by "uplift", where inner
planets are removed by interaction with the outer planets. In these scenarios,
the formation of eccentric warm Jupiters is a signature of a past history of
violent dynamics among massive planets beyond au.Comment: 24 pages, 19 figures. Accepted to MNRA
Monte Carlo Predictions of Far-Infrared Emission from Spiral Galaxies
We present simulations of Far Infrared (FIR) emission by dust in spiral
galaxies, based on the Monte Carlo radiative transfer code of Bianchi, Ferrara
& Giovanardi (1996). The radiative transfer is carried out at several
wavelength in the Ultraviolet, optical and Near Infrared, to cover the range of
the stellar Spectral Energy Distribution (SED). Together with the images of the
galactic model, a map of the energy absorbed by dust is produced. Using
Galactic dust properties, the spatial distribution of dust temperature is
derived under the assumption of thermal equilibrium. A correction is applied
for non-equilibrium emission in the Mid Infrared. Images of dust emission can
then be produced at any wavelength in the FIR.
We show the application of the model to the spiral galaxy NGC 6946. The
observed stellar SED is used as input and models are produced for different
star-dust geometries. It is found that only optically thick dust disks can
reproduce the observed amount of FIR radiation. However, it is not possible to
reproduce the large FIR scalelength suggested by recent observation of spirals
at 200 um, even when the scalelength of the dust disk is larger than that for
stars. Optically thin models have ratios of optical/FIR scalelengths closer to
the 200um observations, but with smaller absolute scalelengths than optically
thick cases. The modelled temperature distributions are compatible with
observations of the Galaxy and other spirals. We finally discuss the
approximations of the model and the impact of a clumpy stellar and dust
structure on the FIR simulations.Comment: 19 pages, 6 figures, accepted by A&
Chlamydia diagnosis rate in England in 2012: an ecological study of local authorities
Objectives Local authorities (LAs) in England commission chlamydia screening as part of the National Chlamydia Screening Programme. It is recommended that LAs achieve a chlamydia diagnosis rate of ≥2300 cases per 100 000 population aged 15–24. We describe national patterns in attainment of the chlamydia diagnosis rate recommendation and possible implications of using it to measure LA-level performance. Methods We used publicly available data sets from England (2012) to explore the association between LAs attaining the recommended chlamydia diagnosis rate and population size, socioeconomic deprivation, test setting and sex. Results We used data from 1 197 121 recorded chlamydia tests in females and 564 117 in males. The chlamydia diagnosis rate recommendation was achieved by 22% (72/324) of LAs overall (43% female population; 8% male population). LAs in the highest deprivation quintile were more likely to reach the recommendation than those in the least-deprived quintile for both sexes (women: unadjusted prevalence ratio (UPR) 7.43, 95% CI 3.65 to 15.11; men: UPR 7.00, 95% CI 1.66 to 29.58). The proportion of tests performed in genitourinary medicine clinics was negatively associated with attainment of the recommended diagnosis rate (UPR 0.95, 0.93 to 0.97). Conclusions Chlamydia diagnosis rate recommendations that reflect local area deprivation (as a proxy for disease burden) may be more appropriate than a single national target if the aim is to reduce health inequalities nationally. We suggest LAs monitor their chlamydia diagnosis rate, test coverage and test positivity across a range of measures (including setting and sex) and pre/post changes to commissioned services. Critical evaluation of performance against the recommendation should be reflected in local commissioning decisions
The ultimate outcome of black hole - neutron star mergers
We present a simple, semi--analytical description for the final stages of
mergers of black hole (BH) -- neutron star (NS) systems. Such systems are of
much interest as gravitational wave sources and gamma--ray burst progenitors.
Numerical studies show that in general the neutron star is not disrupted at the
first phase of mass transfer. Instead, what remains of the neutron star is left
on a wider, eccentric, orbit. We consider the evolution of such systems as they
lose angular momentum via gravitational radiation and come into contact for
further phases of mass transfer. During each mass transfer event the neutron
star mass is reduced until a critical value where mass loss leads to a rapid
increase in the stellar radius. At this point Roche lobe overflow shreds what
remains of the neutron star, most of the mass forming a disc around the black
hole. Such a disc may be massive enough to power a gamma--ray burst. The mass
of the neutron star at the time of disruption (and therefore the disc mass) is
largely independent of the initial masses of the black hole and neutron star,
indicating that BH--NS star mergers may be standard candles.Comment: MNRAS, in pres
Thermodynamic processes generated by a class of completely positive quantum operations
An attempt toward the operational formulation of quantum thermodynamics is
made by employing the recently proposed operations forming positive
operator-valued measures for generating thermodynamic processes. The quantity
of heat as well as the von Neumann entropy monotonically increases under the
operations. The fixed point analysis shows that repeated applications of these
operations to a given system transform from its pure ground state at zero
temperature to the completely random state in the high temperature limit with
intermediate states being generically out of equilibrium. It is shown that the
Clausius inequality can be violated along the processes, in general. A
bipartite spin-1/2 system is analyzed as an explicit example.Comment: 22 pages and 1 figure. Modern Physics Letters B, in pres
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