2,087 research outputs found
Weighted maximal regularity estimates and solvability of non-smooth elliptic systems II
We continue the development, by reduction to a first order system for the
conormal gradient, of \textit{a priori} estimates and solvability for
boundary value problems of Dirichlet, regularity, Neumann type for divergence
form second order, complex, elliptic systems. We work here on the unit ball and
more generally its bi-Lipschitz images, assuming a Carleson condition as
introduced by Dahlberg which measures the discrepancy of the coefficients to
their boundary trace near the boundary. We sharpen our estimates by proving a
general result concerning \textit{a priori} almost everywhere non-tangential
convergence at the boundary. Also, compactness of the boundary yields more
solvability results using Fredholm theory. Comparison between classes of
solutions and uniqueness issues are discussed. As a consequence, we are able to
solve a long standing regularity problem for real equations, which may not be
true on the upper half-space, justifying \textit{a posteriori} a separate work
on bounded domains.Comment: 76 pages, new abstract and few typos corrected. The second author has
changed nam
Recovery of gastric evacuation rate in Atlantic cod Gadus morhua L. surgically implanted with a dummy telemetry devic
Three-body correlations in Borromean halo nuclei
Three-body correlations in the dissociation of two-neutron halo nuclei are
explored using a technique based on intensity interferometry and Dalitz plots.
This provides for the combined treatment of both the n-n and core-n
interactions in the exit channel. As an example, the breakup of 14Be into
12Be+n+n by Pb and C targets has been analysed and the halo n-n separation
extracted. A finite delay between the emission of the neutrons in the reaction
on the C target was observed and is attributed to 13Be resonances populated in
sequential breakup.Comment: 5 pages, 4 figures, submitted to PR
Measuring energy dependent polarization in soft gamma-rays using Compton scattering in PoGOLite
Linear polarization in X- and gamma-rays is an important diagnostic of many
astrophysical sources, foremost giving information about their geometry,
magnetic fields, and radiation mechanisms. However, very few X-ray polarization
measurements have been made, and then only mono-energetic detections, whilst
several objects are assumed to have energy dependent polarization signatures.
In this paper we investigate whether detection of energy dependent polarization
from cosmic sources is possible using the Compton technique, in particular with
the proposed PoGOLite balloon-experiment, in the 25-100 keV range. We use
Geant4 simulations of a PoGOLite model and input photon spectra based on Cygnus
X-1 and accreting magnetic pulsars (100 mCrab). Effective observing times of 6
and 35 hours were simulated, corresponding to a standard and a long duration
flight respectively. Both smooth and sharp energy variations of the
polarization are investigated and compared to constant polarization signals
using chi-square statistics. We can reject constant polarization, with energy,
for the Cygnus X-1 spectrum (in the hard state), if the reflected component is
assumed to be completely polarized, whereas the distinction cannot be made for
weaker polarization. For the accreting pulsar, constant polarization can be
rejected in the case of polarization in a narrow energy band with at least 50%
polarization, and similarly for a negative step distribution from 30% to 0%
polarization.Comment: 11 pages, 12 figures; updated to match version accepted for
publication in Astroparticle Physics (only minor changes
Response to Cult of the "I"
Purpose: The purpose of this paper is to respond to an earlier article in the Journal of Documentation: The Cult of the “I”. / Design/methodology/approach: The method is a form of critical response. / Findings: Numerous problems regarding the The Cult of the “I” article are discussed. / Originality/value: This paper puts forward views about the iSchools Movement
Conical square function estimates in UMD Banach spaces and applications to H-infinity functional calculi
We study conical square function estimates for Banach-valued functions, and
introduce a vector-valued analogue of the Coifman-Meyer-Stein tent spaces.
Following recent work of Auscher-McIntosh-Russ, the tent spaces in turn are
used to construct a scale of vector-valued Hardy spaces associated with a given
bisectorial operator (A) with certain off-diagonal bounds, such that (A) always
has a bounded (H^{\infty})-functional calculus on these spaces. This provides a
new way of proving functional calculus of (A) on the Bochner spaces
(L^p(\R^n;X)) by checking appropriate conical square function estimates, and
also a conical analogue of Bourgain's extension of the Littlewood-Paley theory
to the UMD-valued context. Even when (X=\C), our approach gives refined
(p)-dependent versions of known results.Comment: 28 pages; submitted for publicatio
Crossing the Dripline to 11N Using Elastic Resonance Scattering
The level structure of the unbound nucleus 11N has been studied by 10C+p
elastic resonance scattering in inverse geometry with the LISE3 spectrometer at
GANIL, using a 10C beam with an energy of 9.0 MeV/u. An additional measurement
was done at the A1200 spectrometer at MSU. The excitation function above the
10C+p threshold has been determined up to 5 MeV. A potential-model analysis
revealed three resonance states at energies 1.27 (+0.18-0.05) MeV (Gamma=1.44
+-0.2 MeV), 2.01(+0.15-0.05) MeV, (Gamma=0.84 +-$0.2 MeV) and 3.75(+-0.05) MeV,
(Gamma=0.60 +-0.05 MeV) with the spin-parity assignments I(pi) =1/2+, 1/2- and
5/2+, respectively. Hence, 11N is shown to have a ground state parity inversion
completely analogous to its mirror partner, 11Be. A narrow resonance in the
excitation function at 4.33 (+-0.05) MeV was also observed and assigned
spin-parity 3/2-.Comment: 14 pages, 9 figures, twocolumn Accepted for publication in PR
The Hardness-Intensity Diagram of Cygnus X-3: Revisiting the Radio/X-Ray States
Cygnus X-3 is one of the brightest X-ray and radio sources in the Galaxy, and
is well known for its erratic behaviour in X-rays as well as in the radio,
occasionally producing major radio flares associated with relativistic
ejections. However, even after many years of observations in various wavelength
bands Cyg X-3 still eludes clear physical understanding. Studying different
emission bands simultaneously in microquasars has proved to be a fruitful
approach towards understanding these systems, especially by shedding light on
the accretion disc/jet connection. We continue this legacy by constructing a
hardness-intensity diagram (HID) from archival Rossi X-ray Timing Explorer data
and linking simultaneous radio observations to it. We find that surprisingly
Cyg X-3 sketches a similar shape in the HID to that seen in other transient
black hole X-ray binaries during outburst but with distinct differences.
Together with the results of this analysis and previous studies of Cyg X-3 we
conclude that the X-ray states can be assigned to six distinct states. This
categorization relies heavily on the simultaneous radio observations and we
identify one new X-ray state, the hypersoft state, similar to the ultrasoft
state, which is associated to the quenched radio state during which there is no
or very faint radio emission. Recent observations of GeV flux observed from Cyg
X-3 (Tavani et al. 2009; Fermi LAT Collaboration et al. 2009) during a soft
X-ray and/or radio quenched state at the onset of a major radio flare hint that
a very energetic process is at work during this time, which is also when the
hypersoft X-ray state is observed. In addition, Cyg X-3 shows flaring with a
wide range of hardness.Comment: 17 pages, 9 figures, accepted for publication in MNRA
The detection of neutron clusters
A new approach to the production and detection of bound neutron clusters is
presented. The technique is based on the breakup of beams of very neutron-rich
nuclei and the subsequent detection of the recoiling proton in a liquid
scintillator. The method has been tested in the breakup of 11Li, 14Be and 15B
beams by a C target. Some 6 events were observed that exhibit the
characteristics of a multineutron cluster liberated in the breakup of 14Be,
most probably in the channel 10Be+4n. The various backgrounds that may mimic
such a signal are discussed in detail.Comment: 11 pages, 12 figures, LPCC 01-1
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