1,277 research outputs found
Spectral weight function for the half-filled Hubbard model: a singular value decomposition approach
The singular value decomposition technique is used to reconstruct the
electronic spectral weight function for a half-filled Hubbard model with
on-site repulsion from Quantum Monte Carlo data. A two-band structure
for the single-particle excitation spectrum is found to persist as the lattice
size exceeds the spin-spin correlation length. The observed bands are flat in
the vicinity of the points in the Brillouin zone, in
accordance with experimental data for high-temperature superconducting
compounds.Comment: 4 pages, Revtex
The inverse Laplace transform as the ultimate tool for transverse mass spectra
New high statistics data from the second generation of ultrarelativistic
heavy-ion experiments open up new possibilities in terms of data analysis. To
fully utilize the potential we propose to analyze the -spectra of
hadrons using the inverse Laplace transform. The problems with its inherent
ill-definedness can be overcome and several applications in other fields like
biology, chemistry or optics have already shown its feasability. Moreover, the
method also promises to deliver upper bounds on the total information content
of the spectra, which is of big importance for all other means of analysis.
Here we compute several Laplace inversions from different thermal scenarios,
both analytically and numerically, to test the efficiency of the method.
Especially the case of a two component structure, related to a possible first
order phase transition to a quark gluon plasma, is closer investigated and it
is shown that at least a signal to noise ratio of is necessary to
resolve two individual components.Comment: 13 pages (PostScript, including figures), BNL-NTHES
Dermatosis caused by Corythuca ciliata (Say, 1932) (Heteroptera, Tingidae). Diagnostic and clinical aspects of an unrecognized pseudoparasitosis
The present article discusses three cases of human infestation by Corythuca ciliata (Lace bugs), a parasite of plane trees. The cases were all in the Piedmont region of northwest Italy and the symptoms involved a large number of hives on the subjects? bodies which were scarcely or not at all itchy and which spontaneously cleared up in all the cases in less than 24 hours. It can be concluded that the Lace bug can be an agent of insect-caused dermatosis and this should be considered in examining subjects who visit or live near wooded areas which are infested
Traumatic myiasis from Sarcophaga (Bercaea) cruentata Meigen, 1826 (Diptera, Sarcophagidae) in a hospital environment: reporting of a clinical case following polytrauma
We present a case of cutaneous myiasis occurring in a hospital environment (nosocomial myiasis) in an patient with serious multiple traumas sustained in a motorcycle accident. The agent responsible for the myiasis was identified as Sarcophaga cruen- tata (Meigen 1826). The larvae found in the necrotic wound were removed and the necessary environmental measures were taken to avoid further infestation. Although nonocomial myiasis is a form of parasitosis already cited in the in literature, it is a rare event and worthy of attention to aid in identifying parasitosis in hospitalized subjects in order to expedite proper diagnosis and treatment
Quantum Noise in Multipixel Image Processing
We consider the general problem of the quantum noise in a multipixel
measurement of an optical image. We first give a precise criterium in order to
characterize intrinsic single mode and multimode light. Then, using a
transverse mode decomposition, for each type of possible linear combination of
the pixels' outputs we give the exact expression of the detection mode, i.e.
the mode carrying the noise. We give also the only way to reduce the noise in
one or several simultaneous measurements.Comment: 8 pages and 1 figur
Scaled Gradient Projection Methods for Astronomical Imaging
This book is a collection of 19 articles which reflect the courses given at the Collège de France/Summer school “Reconstruction d'images − Applications astrophysiques“ held in Nice and Fréjus, France, from June 18 to 22, 2012. The articles presented in this volume address emerging concepts and methods that are useful in the complex process of improving our knowledge of the celestial objects, including Earth
A convergent blind deconvolution method for post-adaptive-optics astronomical imaging
In this paper we propose a blind deconvolution method which applies to data
perturbed by Poisson noise. The objective function is a generalized
Kullback-Leibler divergence, depending on both the unknown object and unknown
point spread function (PSF), without the addition of regularization terms;
constrained minimization, with suitable convex constraints on both unknowns, is
considered. The problem is nonconvex and we propose to solve it by means of an
inexact alternating minimization method, whose global convergence to stationary
points of the objective function has been recently proved in a general setting.
The method is iterative and each iteration, also called outer iteration,
consists of alternating an update of the object and the PSF by means of fixed
numbers of iterations, also called inner iterations, of the scaled gradient
projection (SGP) method. The use of SGP has two advantages: first, it allows to
prove global convergence of the blind method; secondly, it allows the
introduction of different constraints on the object and the PSF. The specific
constraint on the PSF, besides non-negativity and normalization, is an upper
bound derived from the so-called Strehl ratio, which is the ratio between the
peak value of an aberrated versus a perfect wavefront. Therefore a typical
application is the imaging of modern telescopes equipped with adaptive optics
systems for partial correction of the aberrations due to atmospheric
turbulence. In the paper we describe the algorithm and we recall the results
leading to its convergence. Moreover we illustrate its effectiveness by means
of numerical experiments whose results indicate that the method, pushed to
convergence, is very promising in the reconstruction of non-dense stellar
clusters. The case of more complex astronomical targets is also considered, but
in this case regularization by early stopping of the outer iterations is
required
Quantum limits of super-resolution in reconstruction of optical objects
We investigate analytically and numerically the role of quantum fluctuations
in reconstruction of optical objects from diffraction-limited images. Taking as
example of an input object two closely spaced Gaussian peaks we demonstrate
that one can improve the resolution in the reconstructed object over the
classical Rayleigh limit. We show that the ultimate quantum limit of resolution
in such reconstruction procedure is determined not by diffraction but by the
signal-to-noise ratio in the input object. We formulate a quantitative measure
of super-resolution in terms of the optical point-spread function of the
system.Comment: 23 pages, 7 figures. Submitted to Physical Review A e-mail:
[email protected]
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