9,946 research outputs found
Editor\u27s Notes
As a nation there is probably no greater dividing point for most Americans than the topic of immigration. For the past eight years the American Congress has sought to establish a comprehensive immigration policy and pass sweeping legislation that seeks to define who is eligible to be an American citizen and resident and who will be ultimately included or excluded in terms of naturalization and citizenship. Recent failed attempts to pass a Dream Act to legitimate scores of immigrant children and young adults who have resided in the United States nearly all their lives, and in many cases have no conception of any other culture or national entity, illustrates both the urgency and complexity of projected legislation. Millions will ultimately be affected in terms of their status and identity
Analysis of a particle antiparticle description of a soliton cellular automaton
We present a derivation of a formula that gives dynamics of an integrable
cellular automaton associated with crystal bases. This automaton is related to
type D affine Lie algebra and contains usual box-ball systems as a special
case. The dynamics is described by means of such objects as carriers,
particles, and antiparticles. We derive it from an analysis of a recently
obtained formula of the combinatorial R (an intertwiner between tensor products
of crystals) that was found in a study of geometric crystals.Comment: LaTeX, 21 pages, 2 figure
Ergonomic Chair Design by Fusing Qualitative and Quantitative Criteria using Interactive Genetic Algorithms
This paper emphasizes the necessity of formally bringing qualitative and
quantitative criteria of ergonomic design together, and provides a novel
complementary design framework with this aim. Within this framework, different
design criteria are viewed as optimization objectives; and design solutions are
iteratively improved through the cooperative efforts of computer and user. The
framework is rooted in multi-objective optimization, genetic algorithms and
interactive user evaluation. Three different algorithms based on the framework
are developed, and tested with an ergonomic chair design problem. The parallel
and multi-objective approaches show promising results in fitness convergence,
design diversity and user satisfaction metrics
Universal fault-tolerant gates on concatenated stabilizer codes
It is an oft-cited fact that no quantum code can support a set of
fault-tolerant logical gates that is both universal and transversal. This no-go
theorem is generally responsible for the interest in alternative universality
constructions including magic state distillation. Widely overlooked, however,
is the possibility of non-transversal, yet still fault-tolerant, gates that
work directly on small quantum codes. Here we demonstrate precisely the
existence of such gates. In particular, we show how the limits of
non-transversality can be overcome by performing rounds of intermediate
error-correction to create logical gates on stabilizer codes that use no
ancillas other than those required for syndrome measurement. Moreover, the
logical gates we construct, the most prominent examples being Toffoli and
controlled-controlled-Z, often complete universal gate sets on their codes. We
detail such universal constructions for the smallest quantum codes, the 5-qubit
and 7-qubit codes, and then proceed to generalize the approach. One remarkable
result of this generalization is that any nondegenerate stabilizer code with a
complete set of fault-tolerant single-qubit Clifford gates has a universal set
of fault-tolerant gates. Another is the interaction of logical qubits across
different stabilizer codes, which, for instance, implies a broadly applicable
method of code switching.Comment: 18 pages + 5 pages appendix, 12 figure
A Fuzzy Logic Based Algorithm for Finding Astronomical Objects in Wide-Angle Frames
Accurate automatic identification of astronomical objects in an imperfect
world of non-linear wide-angle optics, imperfect optics, inaccurately pointed
telescopes, and defect-ridden cameras is not always a trivial first step. In
the past few years, this problem has been exacerbated by the rise of digital
imaging, providing vast digital streams of astronomical images and data. In the
modern age of increasing bandwidth, human identifications are many times
impracticably slow. In order to perform an automatic computer-based analysis of
astronomical frames, a quick and accurate identification of astronomical
objects is required. Such identification must follow a rigorous transformation
from topocentric celestial coordinates into image coordinates on a CCD frame.
This paper presents a fuzzy logic based algorithm that estimates needed
coordinate transformations in a practical setting. Using a training set of
reference stars, the algorithm statically builds a fuzzy logic model. At
runtime, the algorithm uses this model to associate stellar objects visible in
the frames to known-catalogued objects, and generates files that contain
photometry information of objects visible in the frame. Use of this algorithm
facilitates real-time monitoring of stars and bright transients, allowing
identifications and alerts to be issued more reliably. The algorithm is being
implemented by the Night Sky Live all-sky monitoring global network and has
shown itself significantly more reliable than the previously used non-fuzzy
logic algorithm.Comment: Accepted for publication in PAS
Interpolating between the Bose-Einstein and the Fermi-Dirac distributions in odd dimensions
We consider the response of a uniformly accelerated monopole detector that is
coupled to a superposition of an odd and an even power of a quantized, massless
scalar field in flat spacetime in arbitrary dimensions. We show that, when the
field is assumed to be in the Minkowski vacuum, the response of the detector is
characterized by a Bose-Einstein factor in even spacetime dimensions, whereas a
Bose-Einstein as well as a Fermi-Dirac factor appear in the detector response
when the dimension of spacetime is odd. Moreover, we find that, it is possible
to interpolate between the Bose-Einstein and the Fermi-Dirac distributions in
odd spacetime dimensions by suitably adjusting the relative strengths of the
detector's coupling to the odd and the even powers of the scalar field. We
point out that the response of the detector is always thermal and we, finally,
close by stressing the apparent nature of the appearance of the Fermi-Dirac
factor in the detector response.Comment: RevTeX, 7 page
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