25,680 research outputs found
An Advanced, Three-Dimensional Plotting Library for Astronomy
We present a new, three-dimensional (3D) plotting library with advanced
features, and support for standard and enhanced display devices. The library -
S2PLOT - is written in C and can be used by C, C++ and FORTRAN programs on
GNU/Linux and Apple/OSX systems. S2PLOT draws objects in a 3D (x,y,z) Cartesian
space and the user interactively controls how this space is rendered at run
time. With a PGPLOT inspired interface, S2PLOT provides astronomers with
elegant techniques for displaying and exploring 3D data sets directly from
their program code, and the potential to use stereoscopic and dome display
devices. The S2PLOT architecture supports dynamic geometry and can be used to
plot time-evolving data sets, such as might be produced by simulation codes. In
this paper, we introduce S2PLOT to the astronomical community, describe its
potential applications, and present some example uses of the library.Comment: 12 pages, 10 eps figures (higher resolution versions available from
http://astronomy.swin.edu.au/s2plot/paperfigures). The S2PLOT library is
available for download from http://astronomy.swin.edu.au/s2plo
-algebras from planar algebras I: canonical -algebras associated to a planar algebra
From a planar algebra, we give a functorial construction to produce numerous
associated -algebras. Our main construction is a Hilbert -bimodule
with a canonical real subspace which produces Pimsner-Toeplitz, Cuntz-Pimsner,
and generalized free semicircular -algebras. By compressing this system,
we obtain various canonical -algebras, including Doplicher-Roberts
algebras, Guionnet-Jones-Shlyakhtenko algebras, universal
(Toeplitz-)Cuntz-Krieger algebras, and the newly introduced free graph
algebras. This is the first article in a series studying canonical
-algebras associated to a planar algebra.Comment: 47 pages, many figure
Holistic corpus-based dialectology
This paper is concerned with sketching future directions for corpus-based dialectology. We advocate a holistic approach to the study of geographically conditioned linguistic variability, and we present a suitable methodology, 'corpusbased dialectometry', in exactly this spirit. Specifically, we argue that in order to live up to the potential of the corpus-based method, practitioners need to (i) abandon their exclusive focus on individual linguistic features in favor of the study of feature aggregates, (ii) draw on computationally advanced multivariate analysis techniques (such as multidimensional scaling, cluster analysis, and principal component analysis), and (iii) aid interpretation of empirical results by marshalling state-of-the-art data visualization techniques. To exemplify this line of analysis, we present a case study which explores joint frequency variability of 57 morphosyntax features in 34 dialects all over Great Britain
Efficient view point selection for silhouettes of convex polyhedra
AbstractSilhouettes of polyhedra are an important primitive in application areas such as machine vision and computer graphics. In this paper, we study how to select view points of convex polyhedra such that the silhouette satisfies certain properties. Specifically, we give algorithms to find all projections of a convex polyhedron such that a given set of edges, faces and/or vertices appear on the silhouette.We present an algorithm to solve this problem in O(k2) time for k edges. For orthogonal projections, we give an improved algorithm that is fully adaptive in the number l of connected components formed by the edges, and has a time complexity of O(klogk+kl). We then generalize this algorithm to edges and/or faces appearing on the silhouette
Physics, Topology, Logic and Computation: A Rosetta Stone
In physics, Feynman diagrams are used to reason about quantum processes. In
the 1980s, it became clear that underlying these diagrams is a powerful analogy
between quantum physics and topology: namely, a linear operator behaves very
much like a "cobordism". Similar diagrams can be used to reason about logic,
where they represent proofs, and computation, where they represent programs.
With the rise of interest in quantum cryptography and quantum computation, it
became clear that there is extensive network of analogies between physics,
topology, logic and computation. In this expository paper, we make some of
these analogies precise using the concept of "closed symmetric monoidal
category". We assume no prior knowledge of category theory, proof theory or
computer science.Comment: 73 pages, 8 encapsulated postscript figure
The Disunity of Consciousness
It is commonplace for both philosophers and cognitive scientists to express their allegiance to the
"unity of consciousness". This is the claim that a subjectÂs phenomenal consciousness, at any one
moment in time, is a single thing. This view has had a major influence on computational theories
of consciousness. In particular, what we call single-track theories dominate the literature,
theories which contend that our conscious experience is the result of a single consciousness-making
process or mechanism in the brain. We argue that the orthodox view is quite wrong:
phenomenal experience is not a unity, in the sense of being a single thing at each instant. It is a
multiplicity, an aggregate of phenomenal elements, each of which is the product of a distinct
consciousness-making mechanism in the brain. Consequently, cognitive science is in need of a
multi-track theory of consciousness; a computational model that acknowledges both the
manifold nature of experience, and its distributed neural basis
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