22,577 research outputs found
Pilot interaction with automated airborne decision making systems
The use of advanced software engineering methods (e.g., from artificial intelligence) to aid aircraft crews in procedure selection and execution is investigated. Human problem solving in dynamic environments as effected by the human's level of knowledge of system operations is examined. Progress on the development of full scale simulation facilities is also discussed
Giant Flexoelectric Effect in Ferroelectric Epitaxial Thin Films
We report on nanoscale strain gradients in ferroelectric HoMnO3 epitaxial
thin films, resulting in a giant flexoelectric effect. Using grazing-incidence
in-plane X-ray diffraction, we measured strain gradients in the films, which
were 6 or 7 orders of magnitude larger than typical values reported for bulk
oxides. The combination of transmission electron microscopy, electrical
measurements, and electrostatic calculations showed that flexoelectricity
provides a means of tuning the physical properties of ferroelectric epitaxial
thin films, such as domain configurations and hysteresis curves.Comment: Accepted by Phys. Rev. Let
Impact of reionization on CMB polarization tests of slow-roll inflation
Estimates of inflationary parameters from the CMB B-mode polarization
spectrum on the largest scales depend on knowledge of the reionization history,
especially at low tensor-to-scalar ratio. Assuming an incorrect reionization
history in the analysis of such polarization data can strongly bias the
inflationary parameters. One consequence is that the single-field slow-roll
consistency relation between the tensor-to-scalar ratio and tensor tilt might
be excluded with high significance even if this relation holds in reality. We
explain the origin of the bias and present case studies with various tensor
amplitudes and noise characteristics. A more model-independent approach can
account for uncertainties about reionization, and we show that parametrizing
the reionization history by a set of its principal components with respect to
E-mode polarization removes the bias in inflationary parameter measurement with
little degradation in precision.Comment: 9 pages, 6 figures; submitted to Phys. Rev.
Simple Scheme for Efficient Linear Optics Quantum Gates
We describe the construction of a conditional quantum control-not (CNOT) gate
from linear optical elements following the program of Knill, Laflamme and
Milburn [Nature {\bf 409}, 46 (2001)]. We show that the basic operation of this
gate can be tested using current technology. We then simplify the scheme
significantly.Comment: Problems with PDF figures correcte
Better age estimations using UV-optical colours: breaking the age-metallicity degeneracy
We demonstrate that the combination of GALEX UV photometry in the FUV (~1530
angstroms) and NUV (~2310 angstroms) passbands with optical photometry in the
standard U,B,V,R,I filters can efficiently break the age-metallicity
degeneracy. We estimate well-constrained ages, metallicities and their
associated errors for 42 GCs in M31, and show that the full set of
FUV,NUV,U,B,V,R,I photometry produces age estimates that are ~90 percent more
constrained and metallicity estimates that are ~60 percent more constrained
than those produced by using optical filters alone. The quality of the age
constraints is comparable or marginally better than those achieved using a
large number of spectrscopic indices.Comment: Published in MNRAS (2007), 381, L74 (doi:
10.1111/j.1745-3933.2007.00370.x
Exactly Soluble Quantum Wormhole in Two Dimensions
We are presenting a quantum traversable wormhole in an exactly soluble
two-dimensional model. This is different from previous works since the exotic
negative energy that supports the wormhole is generated from the quantization
of classical energy-momentum tensors. This explicit illustration shows the
quantum-mechanical energy can be used as a candidate for the exotic source. As
for the traversability, after a particle travels through the wormhole, the
static initial wormhole geometry gets a back reaction which spoils the wormhole
structure. However, it may still maintain the initial structure along with the
appropriate boundary condition.Comment: v1. 13 pages, 1 figure, REVTeX3; v2. 1 Ref. added, REVTeX4, to appear
in Phys. Rev.
Rotating Black Hole Entropy from Two Different Viewpoints
Using the brick-wall method, we study the entropy of Kerr-Newman black hole
from two different viewpoints, a rest observer at infinity and zero angular
momentum observer near horizon. We investigate this with scalar field in the
canonical quantization approach. An observer at infinity can take one of the
two possible frequency ranges; one is with positive frequencies only and the
other is with the whole range including negative frequencies. On the other
hand, a zero angular momentum observer near horizon can take positive
frequencies only. For the observer at infinity the superradiant modes appear in
either choice of the frequency ranges and the two results coincide. For the
zero angular momentum observer superradiant modes do not appear due to absence
of ergoregion. The resulting entropies from the two viewpoints turn out to be
the same.Comment: LaTeX 18 pages, 2 figures, Minor modifications in section 3(ZAMO
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