58,550 research outputs found
The S2 VLBI Correlator: A Correlator for Space VLBI and Geodetic Signal Processing
We describe the design of a correlator system for ground and space-based
VLBI. The correlator contains unique signal processing functions: flexible LO
frequency switching for bandwidth synthesis; 1 ms dump intervals, multi-rate
digital signal-processing techniques to allow correlation of signals at
different sample rates; and a digital filter for very high resolution
cross-power spectra. It also includes autocorrelation, tone extraction, pulsar
gating, signal-statistics accumulation.Comment: 44 pages, 13 figure
Constructing Qubits in Physical Systems
The notion of a qubit is ubiquitous in quantum information processing. In
spite of the simple abstract definition of qubits as two-state quantum systems,
identifying qubits in physical systems is often unexpectedly difficult. There
are an astonishing variety of ways in which qubits can emerge from devices.
What essential features are required for an implementation to properly
instantiate a qubit? We give three typical examples and propose an operational
characterization of qubits based on quantum observables and subsystems.Comment: 16 pages, no figures; IoP LaTeX2e style. Submitted to J. Phys. A:
Math. Ge
Web-Based Visualization of Very Large Scientific Astronomy Imagery
Visualizing and navigating through large astronomy images from a remote
location with current astronomy display tools can be a frustrating experience
in terms of speed and ergonomics, especially on mobile devices. In this paper,
we present a high performance, versatile and robust client-server system for
remote visualization and analysis of extremely large scientific images.
Applications of this work include survey image quality control, interactive
data query and exploration, citizen science, as well as public outreach. The
proposed software is entirely open source and is designed to be generic and
applicable to a variety of datasets. It provides access to floating point data
at terabyte scales, with the ability to precisely adjust image settings in
real-time. The proposed clients are light-weight, platform-independent web
applications built on standard HTML5 web technologies and compatible with both
touch and mouse-based devices. We put the system to the test and assess the
performance of the system and show that a single server can comfortably handle
more than a hundred simultaneous users accessing full precision 32 bit
astronomy data.Comment: Published in Astronomy & Computing. IIPImage server available from
http://iipimage.sourceforge.net . Visiomatic code and demos available from
http://www.visiomatic.org
Collinearly improved JIMWLK evolution in Langevin form
The high-energy evolution of Wilson line operators, which at leading order is
described by the Balitsky-JIMWLK equations, receives large radiative
corrections enhanced by single and double collinear logarithms at
next-to-leading order and beyond. We propose a method for resumming such
logarithmic corrections to all orders, at the level of the Langevin formulation
of the JIMWLK equation. The ensuing, collinearly-improved Langevin equation
features generalized Wilson line operators, which depend not only upon rapidity
(the logarithm of the longitudinal momentum), but also upon the transverse size
of the color neutral projectile to which the Wilson lines belong. This
additional scale dependence is built up during the evolution, via the condition
that the successive emissions of soft gluons be ordered in time. The presence
of this transverse scale in the Langevin equation furthermore allows for the
resummation of the one-loop running coupling corrections.Comment: 24 pages, 1 figur
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