9,941 research outputs found
Mass spectrum and elastic scattering in the massive SU(2)_f Schwinger model on the lattice
We calculate numerically scattering phases for elastic meson-meson scattering
processes in the strongly coupled massive Schwinger-model with an SU(2) flavour
symmetry. These calculations are based on Luescher's method in which finite
size effects in two-particle energies are exploited. The results from
Monte-Carlo simulations with staggered fermions for the lightest meson ("pion")
are in good agreement with the analytical strong-coupling prediction.
Furthermore, the mass spectrum of low-lying mesonic states is investigated
numerically. We find a surprisingly rich spectrum in the mass region [m_\pi,4
m_\pi].Comment: 43 pages, 15 figures, LaTeX, uses feynmf.st
Communication and correlation among communities
Given a network and a partition in communities, we consider the issues "how
communities influence each other" and "when two given communities do
communicate". Specifically, we address these questions in the context of
small-world networks, where an arbitrary quenched graph is given and long range
connections are randomly added. We prove that, among the communities, a
superposition principle applies and gives rise to a natural generalization of
the effective field theory already presented in [Phys. Rev. E 78, 031102]
(n=1), which here (n>1) consists in a sort of effective TAP (Thouless, Anderson
and Palmer) equations in which each community plays the role of a microscopic
spin. The relative susceptibilities derived from these equations calculated at
finite or zero temperature, where the method provides an effective percolation
theory, give us the answers to the above issues. Unlike the case n=1,
asymmetries among the communities may lead, via the TAP-like structure of the
equations, to many metastable states whose number, in the case of negative
short-cuts among the communities, may grow exponentially fast with n. As
examples we consider the n Viana-Bray communities model and the n
one-dimensional small-world communities model. Despite being the simplest ones,
the relevance of these models in network theory, as e.g. in social networks, is
crucial and no analytic solution were known until now. Connections between
percolation and the fractal dimension of a network are also discussed. Finally,
as an inverse problem, we show how, from the relative susceptibilities, a
natural and efficient method to detect the community structure of a generic
network arises.
For a short presentation of the main result see arXiv:0812.0608.Comment: 29 pages, 5 figure
An extensive English language bibliography on graph theory and its applications, supplement 1
Graph theory and its applications - bibliography, supplement
An extensive English language bibliography on graph theory and its applications
Bibliography on graph theory and its application
Engineering Object-Oriented Semantics Using Graph Transformations
In this paper we describe the application of the theory of graph transformations to the practise of language design. We have defined the semantics of a small but realistic object-oriented language (called TAAL) by mapping the language constructs to graphs and their operational semantics to graph transformation rules. In the process we establish a mapping between UML models and graphs.
TAAL was developed for the purpose of this paper, as an extensive case study in engineering object-oriented language semantics using graph transformation. It incorporates the basic aspects of many commonly used object-oriented programming languages: apart from essential imperative programming constructs, it includes inheritance, object creation and method overriding. The language specification is based on a number of meta-models written in UML.
Both the static and dynamic semantics are defined using graph rewriting rules.
In the course of the case study, we have built an Eclipse plug-in that automatically transforms arbitrary TAAL programs into graphs, in a graph format readable by another tool. This second tool is called Groove, and it is able to execute graph transformations. By combining both tools we are able to visually simulate the execution of any TAAL program
Signal Flow Graph Approach to Efficient DST I-IV Algorithms
In this paper, fast and efficient discrete sine transformation (DST)
algorithms are presented based on the factorization of sparse, scaled
orthogonal, rotation, rotation-reflection, and butterfly matrices. These
algorithms are completely recursive and solely based on DST I-IV. The presented
algorithms have low arithmetic cost compared to the known fast DST algorithms.
Furthermore, the language of signal flow graph representation of digital
structures is used to describe these efficient and recursive DST algorithms
having points signal flow graph for DST-I and points signal flow
graphs for DST II-IV
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