13,798 research outputs found
Reconstruction of the phase of matter-wave fields using a momentum resolved cross-correlation technique
We investigate the potential of the so-called XFROG cross-correlation
technique originally developed for ultrashort laser pulses for the recovery of
the amplitude and phase of the condensate wave function of a Bose-Einstein
condensate. Key features of the XFROG method are its high resolution,
versatility and stability against noise and some sources of systematic errors.
After showing how an analogue of XFROG can be realized for Bose-Einstein
condensates, we illustrate its effectiveness in determining the amplitude and
phase of the wave function of a vortex state. The impact of a reduction of the
number of measurements and of typical sources of noise on the field
reconstruction are also analyzed.Comment: 7 pages; 9 figures; article with higher resolution figures available
from author
An improved solar wind electron-density model for pulsar timing
Variations in the solar wind density introduce variable delays into pulsar
timing observations. Current pulsar timing analysis programs only implement
simple models of the solar wind, which not only limit the timing accuracy, but
can also affect measurements of pulsar rotational, astrometric and orbital
parameters. We describe a new model of the solar wind electron density content
which uses observations from the Wilcox Solar Observatory of the solar magnetic
field. We have implemented this model into the tempo2 pulsar timing package. We
show that this model is more accurate than previous models and that these
corrections are necessary for high precision pulsar timing applications.Comment: Accepted by ApJ, 13 pages, 4 figure
A Variational Expansion for the Free Energy of a Bosonic System
In this paper, a variational perturbation scheme for nonrelativistic
many-Fermion systems is generalized to a Bosonic system. By calculating the
free energy of an anharmonic oscillator model, we investigated this variational
expansion scheme for its efficiency. Using the modified Feynman rules for the
diagrams, we obtained the analytical expression of the free energy up to the
fourth order. Our numerical results at various orders are compared with the
exact and other relevant results.Comment: 9 pages, 3 EPS figures. With a few typo errors corrected. to appear
in J. Phys.
Tube choledochoureterostomy: A simple method for bile diversion
A technique of bile diversion by tube choledochoureterostomy has been devised for the purpose of studying the role of bile in the intestinal absorption of drugs. This method was used in six dogs. No technical difficulties or major complications developed, as are inevitable with alternative methods, including external fistula. © 1990 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted
Non-Markovian entanglement dynamics in coupled superconducting qubit systems
We theoretically analyze the entanglement generation and dynamics by coupled
Josephson junction qubits. Considering a current-biased Josephson junction
(CBJJ), we generate maximally entangled states. In particular, the entanglement
dynamics is considered as a function of the decoherence parameters, such as the
temperature, the ratio between the reservoir cutoff
frequency and the system oscillator frequency , % between
the characteristic frequency of the %quantum system of interest, and
the cut-off frequency of %Ohmic reservoir and the energy levels
split of the superconducting circuits in the non-Markovian master equation. We
analyzed the entanglement sudden death (ESD) and entanglement sudden birth
(ESB) by the non-Markovian master equation. Furthermore, we find that the
larger the ratio and the thermal energy , the shorter the
decoherence. In this superconducting qubit system we find that the entanglement
can be controlled and the ESD time can be prolonged by adjusting the
temperature and the superconducting phases which split the energy
levels.Comment: 13 pages, 3 figure
Status Update of the Parkes Pulsar Timing Array
The Parkes Pulsar Timing Array project aims to make a direct detection of a
gravitational-wave background through timing of millisecond pulsars. In this
article, the main requirements for that endeavour are described and recent and
ongoing progress is outlined. We demonstrate that the timing properties of
millisecond pulsars are adequate and that technological progress is timely to
expect a successful detection of gravitational waves within a decade, or
alternatively to rule out all current predictions for gravitational wave
backgrounds formed by supermassive black-hole mergers.Comment: 10 pages, 3 figures, Amaldi 8 conference proceedings, accepted by
Classical & Quantum Gravit
Classification-reconstruction learning for open-set recognition
Open-set classification is a problem of handling `unknown' classes that are
not contained in the training dataset, whereas traditional classifiers assume
that only known classes appear in the test environment. Existing open-set
classifiers rely on deep networks trained in a supervised manner on known
classes in the training set; this causes specialization of learned
representations to known classes and makes it hard to distinguish unknowns from
knowns. In contrast, we train networks for joint classification and
reconstruction of input data. This enhances the learned representation so as to
preserve information useful for separating unknowns from knowns, as well as to
discriminate classes of knowns. Our novel Classification-Reconstruction
learning for Open-Set Recognition (CROSR) utilizes latent representations for
reconstruction and enables robust unknown detection without harming the
known-class classification accuracy. Extensive experiments reveal that the
proposed method outperforms existing deep open-set classifiers in multiple
standard datasets and is robust to diverse outliers. The code is available in
https://nae-lab.org/~rei/research/crosr/.Comment: 11 pages, 7 figure
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