16,085 research outputs found
Complex Structures Defined on Dynamically Triangulated Surfaces
A method to define the complex structure and separate the conformal mode is
proposed for a surface constructed by two-dimensional dynamical triangulation.
Applications are made for surfaces coupled to matter fields such as scalar
fields ( and ) and Ising spins ( and ). We observe a
well-defined complex structure for cases when the matter central charges are
less than and equal to one, while it becomes unstable beyond . This can be
regarded as the transition expected in analytic theories.Comment: 8 pages, 5 Postscript figure
Merlin: A Language for Provisioning Network Resources
This paper presents Merlin, a new framework for managing resources in
software-defined networks. With Merlin, administrators express high-level
policies using programs in a declarative language. The language includes
logical predicates to identify sets of packets, regular expressions to encode
forwarding paths, and arithmetic formulas to specify bandwidth constraints. The
Merlin compiler uses a combination of advanced techniques to translate these
policies into code that can be executed on network elements including a
constraint solver that allocates bandwidth using parameterizable heuristics. To
facilitate dynamic adaptation, Merlin provides mechanisms for delegating
control of sub-policies and for verifying that modifications made to
sub-policies do not violate global constraints. Experiments demonstrate the
expressiveness and scalability of Merlin on real-world topologies and
applications. Overall, Merlin simplifies network administration by providing
high-level abstractions for specifying network policies and scalable
infrastructure for enforcing them
Adaptive computation of gravitational waves from black hole interactions
We construct a class of linear partial differential equations describing
general perturbations of non-rotating black holes in 3D Cartesian coordinates.
In contrast to the usual approach, a single equation treats all radiative modes simultaneously, allowing the study of wave perturbations of black
holes with arbitrary 3D structure, as would be present when studying the full
set of nonlinear Einstein equations describing a perturbed black hole. This
class of equations forms an excellent testbed to explore the computational
issues of simulating black spacetimes using a three dimensional adaptive mesh
refinement code. Using this code, we present results from the first fully
resolved 3D solution of the equations describing perturbed black holes. We
discuss both fixed and adaptive mesh refinement, refinement criteria, and the
computational savings provided by adaptive techniques in 3D for such model
problems of distorted black holes.Comment: 16 Pages, RevTeX, 13 figure
MAGDA: A Mobile Agent based Grid Architecture
Mobile agents mean both a technology
and a programming paradigm. They allow for a
flexible approach which can alleviate a number
of issues present in distributed and Grid-based
systems, by means of features such as migration,
cloning, messaging and other provided mechanisms.
In this paper we describe an architecture
(MAGDA – Mobile Agent based Grid Architecture)
we have designed and we are currently
developing to support programming and execution
of mobile agent based application upon Grid
systems
Flat directions, doublet-triplet splitting, the monopole problem, and all that
We discuss a supersymmetric SU(6) grand unified theory with the GUT flat
direction being lifted by soft supersymmetry breaking, and the doublet-triplet
splitting being achieved with Higgs as a pseudo-Goldstone boson. The theory
offers a simple solution to the false vacuum and monopole problems.Comment: Latex, 11 pages, no figures. Improved version, more discussion on
1/M_Pl corrections and unwanted relics, new reference
Tools for Thought: The Case of Mathematics
The objective of this article is to take into account the functioning of representational cognitive tools, and in particular of notations and visualizations in mathematics. In order to explain their functioning, formulas in algebra and logic and diagrams in topology will be presented as case studies and the notion of manipulative imagination as proposed in previous work will be discussed. To better characterize the analysis, the notions of material anchor and representational affordance will be introduced
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