85,401 research outputs found
The introduction of a ward-based medical team system within a General and Emergency Medical Directorate
The GL-l.u.st.\ constant and asymmetry of the Kalton-Peck twisted sum in finite dimensions
We prove that the Kalton-Peck twisted sum of -dimensional Hilbert
spaces has GL-l.u.st.\ constant of order and bounded GL constant. This
is the first concrete example which shows different explicit orders of growth
in the GL and GL-l.u.st.\ constants. We discuss also the asymmetry constants of
Cross Calibration of Imaging Air Cherenkov Telescopes with Fermi
An updated model for the synchrotron and inverse Compton emission from a
population of high energy electrons of the Crab Nebula is used to reproduce the
measured spectral energy distribution from radio to high energy gamma-rays. By
comparing the predicted inverse Compton component with recent Fermi
measurements of the nebula's emission, it is possible to determine the average
magnetic field in the nebula and to derive the underlying electron energy
distribution. The model calculation can then be used to cross calibrate the
Fermi observations with ground based air shower measurements. The resulting
energy calibration factors are derived and can be used for combining broad
energy measurements taken with Fermi in conjunction with ground based
measurements.Comment: 2009 Fermi Symposium, eConf Proceedings C091122, 5 pages, 5 figures,
3 table
Rotational properties of two-component Bose gases in the lowest Landau level
We study the rotational (yrast) spectra of dilute two-component atomic Bose
gases in the low angular momentum regime, assuming equal interspecies and
intraspecies interaction. Our analysis employs the composite fermion (CF)
approach including a pseudospin degree of freedom. While the CF approach is not
{\it a priori} expected to work well in this angular momentum regime, we show
that composite fermion diagonalization gives remarkably accurate approximations
to low energy states in the spectra. For angular momenta (where
and denote the numbers of particles of the two species, and ), we
find that the CF states span the full Hilbert space and provide a convenient
set of basis states which, by construction, are eigenstates of the symmetries
of the Hamiltonian. Within this CF basis, we identify a subset of the basis
states with the lowest -level kinetic energy. Diagonalization within
this significally smaller subspace constitutes a major computational
simplification and provides very close approximations to ground states and a
number of low-lying states within each pseudospin and angular momentum channel
Non-equilibrium Josephson effect through helical edge states
We study Josephson junctions between superconductors connected through the
helical edge states of a two-dimensional topological insulator in the presence
of a magnetic barrier. As the equilibrium Andreev bound states of the junction
are 4Pi-periodic in the superconducting phase difference, it was speculated
that, at finite dc bias voltage, the junction exhibits a fractional Josephson
effect with half the Josephson frequency. Using the scattering matrix
formalism, we show that signatures of this effect can be seen in the
finite-frequency current noise. Furthermore, we discuss other manifestations of
the Majorana bound states forming at the edges of the superconductors.Comment: 4+ pages, 3 figure
Neutrino Capture and r-Process Nucleosynthesis
We explore neutrino capture during r-process nucleosynthesis in
neutrino-driven ejecta from nascent neutron stars. We focus on the interplay
between charged-current weak interactions and element synthesis, and we
delineate the important role of equilibrium nuclear dynamics. During the period
of coexistence of free nucleons and light and/or heavy nuclei, electron
neutrino capture inhibits the r-process. At all stages, capture on free
neutrons has a larger impact than capture on nuclei. However, neutrino capture
on heavey nuclei by itself, if it is very strong, is also detrimental to the
r-process until large nuclear equilibrium clusters break down and the classical
neutron-capture phase of the r-process begins. The sensitivity of the r-process
to neutrino irradiation means that neutrino-capture effects can strongly
constrain the r-process site, neutrino physics, or both. These results apply
also to r-process scenarios other than neutrino-heated winds.Comment: 20 pages, 17 figures, Submitted to Physical Review
Quantum critical fluctuations in disordered d-wave superconductors
Quasiparticles in the cuprates appear to be subject to anomalously strong
inelastic damping mechanisms. To explain the phenomenon, Sachdev and
collaborators recently proposed to couple the system to a critically
fluctuating order parameter mode of either id_{xy}- or is-symmetry. Motivated
by the observation that the energies relevant for the dynamics of this mode are
comparable to the scattering rate induced by even moderate impurity
concentrations, we here generalize the approach to the presence of static
disorder. In the id-case, we find that the coupling to disorder renders the
order parameter dynamics diffusive but otherwise leaves much of the
phenomenology observed in the clean case intact. In contrast, the interplay of
impurity scattering and order parameter fluctuations of is-symmetry entails the
formation of a secondary superconductor transition, with a critical temperature
exponentially sensitive to the disorder concentration.Comment: 4 pages, 2 figures include
Depletion of molecular gas by an accretion outburst in a protoplanetary disk
We investigate new and archival 3-5 m high resolution ( km
s) spectroscopy of molecular gas in the inner disk of the young
solar-mass star EX Lupi, taken during and after the strong accretion outburst
of 2008. The data were obtained using the CRIRES spectrometer at the ESO Very
Large Telescope in 2008 and 2014. In 2008, emission lines from CO, HO,
and OH were detected with broad profiles tracing gas near and within the
corotation radius (0.02-0.3 AU). In 2014, the spectra display marked
differences. The CO lines, while still detected, are much weaker, and the
HO and OH lines have disappeared altogether. At 3 m a veiled stellar
photospheric spectrum is observed. Our analysis finds that the molecular gas
mass in the inner disk has decreased by an order of magnitude since the
outburst, matching a similar decrease in the accretion rate onto the star. We
discuss these findings in the context of a rapid depletion of material
accumulated beyond the disk corotation radius during quiescent periods, as
proposed by models of episodic accretion in EXor type young stars.Comment: 6 pages, 4 figures, 1 table, accepted for publication in the
Astrophysical Journal Letter
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