1,637,721 research outputs found
Adaptive Mesh Refinement for Characteristic Codes
The use of adaptive mesh refinement (AMR) techniques is crucial for accurate
and efficient simulation of higher dimensional spacetimes. In this work we
develop an adaptive algorithm tailored to the integration of finite difference
discretizations of wave-like equations using characteristic coordinates. We
demonstrate the algorithm by constructing a code implementing the
Einstein-Klein-Gordon system of equations in spherical symmetry. We discuss how
the algorithm can trivially be generalized to higher dimensional systems, and
suggest a method that can be used to parallelize a characteristic code.Comment: 36 pages, 17 figures; updated to coincide with journal versio
Kranc: a Mathematica application to generate numerical codes for tensorial evolution equations
We present a suite of Mathematica-based computer-algebra packages, termed
"Kranc", which comprise a toolbox to convert (tensorial) systems of partial
differential evolution equations to parallelized C or Fortran code. Kranc can
be used as a "rapid prototyping" system for physicists or mathematicians
handling very complicated systems of partial differential equations, but
through integration into the Cactus computational toolkit we can also produce
efficient parallelized production codes. Our work is motivated by the field of
numerical relativity, where Kranc is used as a research tool by the authors. In
this paper we describe the design and implementation of both the Mathematica
packages and the resulting code, we discuss some example applications, and
provide results on the performance of an example numerical code for the
Einstein equations.Comment: 24 pages, 1 figure. Corresponds to journal versio
State-of-the-art in Power Line Communications: from the Applications to the Medium
In recent decades, power line communication has attracted considerable
attention from the research community and industry, as well as from regulatory
and standardization bodies. In this article we provide an overview of both
narrowband and broadband systems, covering potential applications, regulatory
and standardization efforts and recent research advancements in channel
characterization, physical layer performance, medium access and higher layer
specifications and evaluations. We also identify areas of current and further
study that will enable the continued success of power line communication
technology.Comment: 19 pages, 12 figures. Accepted for publication, IEEE Journal on
Selected Areas in Communications. Special Issue on Power Line Communications
and its Integration with the Networking Ecosystem. 201
On convergence of higher order schemes for the projective integration method for stiff ordinary differential equations
We present a convergence proof for higher order implementations of the
projective integration method (PI) for a class of deterministic multi-scale
systems in which fast variables quickly settle on a slow manifold. The error is
shown to contain contributions associated with the length of the microsolver,
the numerical accuracy of the macrosolver and the distance from the slow
manifold caused by the combined effect of micro- and macrosolvers,
respectively. We also provide stability conditions for the PI methods under
which the fast variables will not diverge from the slow manifold. We
corroborate our results by numerical simulations.Comment: 43 pages, 7 figures; accepted for publication in the Journal of
Computational and Applied Mathematic
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