3,025 research outputs found
Scalar mesons above and below 1 GeV
We show that two nonets and a glueball provide a consistent description of
data on scalar mesons below 1.7 GeV. Above 1 GeV the states form a conventional
(q bar q) nonet mixed with the glueball of lattice QCD. Below 1 GeV the states
also form a nonet, as implied by the attractive forces of QCD, but of more
complicated nature. Near the center they are 4 quark states of the Jaffe type
in S-wave, with some (q bar q) in P-wave, but further out they rearrange in
colour to two colourless (q bar q) pairs and finally as meson-meson states. A
simple effective chiral model for such a system with two scalar nonets can be
made involving two coupled linear sigma models. One of these could be looked
upon as the Higgs sector of nonpertubative QCD.Comment: 34 pages in Latex, minor improvements in sec
Error Metrics for Learning Reliable Manifolds from Streaming Data
Spectral dimensionality reduction is frequently used to identify
low-dimensional structure in high-dimensional data. However, learning
manifolds, especially from the streaming data, is computationally and memory
expensive. In this paper, we argue that a stable manifold can be learned using
only a fraction of the stream, and the remaining stream can be mapped to the
manifold in a significantly less costly manner. Identifying the transition
point at which the manifold is stable is the key step. We present error metrics
that allow us to identify the transition point for a given stream by
quantitatively assessing the quality of a manifold learned using Isomap. We
further propose an efficient mapping algorithm, called S-Isomap, that can be
used to map new samples onto the stable manifold. We describe experiments on a
variety of data sets that show that the proposed approach is computationally
efficient without sacrificing accuracy
Matching Parton Showers and Matrix Elements
We compare different procedures for combining fixed-order tree-level matrix
element generators with parton showers. We use the case of W-production at the
Tevatron and the LHC to compare different implementations of the so-called CKKW
scheme and one based on the so-called MLM scheme using different matrix element
generators and different parton cascades. We find that although similar results
are obtained in all cases, there are important differences.Comment: Proceedings of the "HERA and the LHC" workshop, CERN/DESY 2004/200
Plateaus can be harder in multi-objective optimization
AbstractIn recent years a lot of progress has been made in understanding the behavior of evolutionary computation methods for single- and multi-objective problems. Our aim is to analyze the diversity mechanisms that are implicitly used in evolutionary algorithms for multi-objective problems by rigorous runtime analyses. We show that, even if the population size is small, the runtime can be exponential where corresponding single-objective problems are optimized within polynomial time. To illustrate this behavior we analyze a simple plateau function in a first step and extend our result to a class of instances of the well-known SetCover problem
Woven Rope Friezes
Here we present a complete set of recipes showing how to construct smooth curves with any desired frieze symmetry; we provide examples woven by Rossing for many of the pattern types, and invite readers to make others. We review the concept of frieze symmetry, develop the formulas for parametric equations with given symmetries, and pose some open questions raised by our analysis
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