8,875 research outputs found
The International Mass Loading Service
The International Mass Loading Service computes four loadings: a) atmospheric
pressure loading; b) land water storage loading; c) oceanic tidal loading; and
d) non-tidal oceanic loading. The service provides to users the mass loading
time series in three forms: 1) pre-computed time series for a list of 849 space
geodesy stations; 2) pre-computed time series on the global 1deg x 1deg grid;
and 3) on-demand Internet service for a list of stations and a time range
specified by the user. The loading displacements are provided for the time
period from 1979.01.01 through present, updated on an hourly basis, and have
latencies 8-20 hours.Comment: 8 pages, 3 figures, to appear in the Proceedings of the Reference
Frames for Applications in Geosciences Simposium, held in Luxemboug in
October 201
Potential impacts of sea level rise on mangroves in Ca Mau Cape, south Vietnam: An application of remote sensing techniques for assessment
ADL: a graphical design language for real time parallel applications
Designing parallel applications is generally experienced as a tedious and difficult task, especially when hard real-time performance requirements have to be met. This paper
discusses on-going work concerning the construction of a Design Entry System which
supports the design phase of parallel real-time industrial application development. In
particular, in this paper we pay attention to the development and implementation of a
graphical Application Design Language. The work is part of the ESPRIT project Hamlet which
focuses on industrial application of transputer-based systems for commercially strategic
real-time applications
The Hamlet design entry system: an overview of ADL and its environment
Exploiting parallelism for industrial real-time applications has not received much attention compared to scientific applications. The available real-time design methods do not adequately address the issue of parallelism, resulting still in a strong need for low-level tools such as debuggers and monitors. This need illustrates that developing parallel real-time applications is indeed a difficult and tedious task. In this paper we show how problems can be alleviated if an approach is followed that allows for experimentation with designs and implementations. In particular, we discuss a development system that integrates design, implementation, execution, and analysis of real-time applications, putting emphasis on exploitation of parallelism. In the paper we primarily concentrate on the support for application *design*, as we feel that parallelism should essentially be addressed at this level
Algorithmic approach to adiabatic quantum optimization
It is believed that the presence of anticrossings with exponentially small
gaps between the lowest two energy levels of the system Hamiltonian, can render
adiabatic quantum optimization inefficient. Here, we present a simple adiabatic
quantum algorithm designed to eliminate exponentially small gaps caused by
anticrossings between eigenstates that correspond with the local and global
minima of the problem Hamiltonian. In each iteration of the algorithm,
information is gathered about the local minima that are reached after passing
the anticrossing non-adiabatically. This information is then used to penalize
pathways to the corresponding local minima, by adjusting the initial
Hamiltonian. This is repeated for multiple clusters of local minima as needed.
We generate 64-qubit random instances of the maximum independent set problem,
skewed to be extremely hard, with between 10^5 and 10^6 highly-degenerate local
minima. Using quantum Monte Carlo simulations, it is found that the algorithm
can trivially solve all the instances in ~10 iterations.Comment: 7 pages, 3 figure
Neutrix Calculus and Finite Quantum Field Theory
In general, quantum field theories (QFT) require regularizations and infinite
renormalizations due to ultraviolet divergences in their loop calculations.
Furthermore, perturbation series in theories like QED are not convergent
series, but are asymptotic series. We apply neutrix calculus, developed in
connection with asymptotic series and divergent integrals, to QFT,obtaining
finite renormalizations. While none of the physically measurable results in
renormalizable QFT is changed, quantum gravity is rendered more manageable in
the neutrix framework.Comment: 10 pages; LaTeX; version to appear in J. Phys. A: Math. Gen. as a
Letter to the Edito
Probing spacetime foam with extragalactic sources
Due to quantum fluctuations, spacetime is probably ``foamy'' on very small
scales. We propose to detect this texture of spacetime foam by looking for
core-halo structures in the images of distant quasars. We find that the Very
Large Telescope interferometer will be on the verge of being able to probe the
fabric of spacetime when it reaches its design performance. Our method also
allows us to use spacetime foam physics and physics of computation to infer the
existence of dark energy/matter, independent of the evidence from recent
cosmological observations.Comment: LaTeX, 11 pages, 1 figure; version submitted to PRL; several
references added; very useful comments and suggestions by Eric Perlman
incorporate
Classical and Quantum Annealing in the Median of Three Satisfiability
We determine the classical and quantum complexities of a specific ensemble of
three-satisfiability problems with a unique satisfying assignment for up to
N=100 and N=80 variables, respectively. In the classical limit we employ
generalized ensemble techniques and measure the time that a Markovian Monte
Carlo process spends in searching classical ground states. In the quantum limit
we determine the maximum finite correlation length along a quantum adiabatic
trajectory determined by the linear sweep of the adiabatic control parameter in
the Hamiltonian composed of the problem Hamiltonian and the constant transverse
field Hamiltonian. In the median of our ensemble both complexities diverge
exponentially with the number of variables. Hence, standard, conventional
adiabatic quantum computation fails to reduce the computational complexity to
polynomial. Moreover, the growth-rate constant in the quantum limit is 3.8
times as large as the one in the classical limit, making classical fluctuations
more beneficial than quantum fluctuations in ground-state searches
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