3,122 research outputs found
Noncommutative Geometry as a Regulator
We give a perturbative quantization of space-time in the case where the
commutators of the underlying algebra
generators are not central . We argue that this kind of quantum space-times can
be used as regulators for quantum field theories . In particular we show in the
case of the theory that by choosing appropriately the commutators
we can remove all the infinities by reproducing all the
counter terms . In other words the renormalized action on plus the
counter terms can be rewritten as only a renormalized action on the quantum
space-time . We conjecture therefore that renormalization of quantum
field theory is equivalent to the quantization of the underlying space-time
.Comment: Latex, 30 pages, no figures,typos corrected,references added .
Substantial amount of rewriting of the last section . Final interesting
remarks added at the end of the pape
GraphMaps: Browsing Large Graphs as Interactive Maps
Algorithms for laying out large graphs have seen significant progress in the
past decade. However, browsing large graphs remains a challenge. Rendering
thousands of graphical elements at once often results in a cluttered image, and
navigating these elements naively can cause disorientation. To address this
challenge we propose a method called GraphMaps, mimicking the browsing
experience of online geographic maps.
GraphMaps creates a sequence of layers, where each layer refines the previous
one. During graph browsing, GraphMaps chooses the layer corresponding to the
zoom level, and renders only those entities of the layer that intersect the
current viewport. The result is that, regardless of the graph size, the number
of entities rendered at each view does not exceed a predefined threshold, yet
all graph elements can be explored by the standard zoom and pan operations.
GraphMaps preprocesses a graph in such a way that during browsing, the
geometry of the entities is stable, and the viewer is responsive. Our case
studies indicate that GraphMaps is useful in gaining an overview of a large
graph, and also in exploring a graph on a finer level of detail.Comment: submitted to GD 201
A D=4 N=1 Orbifold of Type I Strings
We consider the propagation of Type I open superstrings on orbifolds with
four non-compact dimensions and supersymmetry. In this paper, we
concentrate on a non-trivial Z_2xZ_2 example. We show that consistency
conditions, arising from tadpole cancellation and algebraic sources, require
the existence of three sets of Dirichlet 5-branes. We discuss fully the
enhancements of the spectrum when these 5-branes intersect. An amusing
attribute of these models is the importance of the tree-level (in Type I
language) superpotential to the consistent relationship between Higgsing and
the motions of 5-branes.Comment: 24 pages, uses LaTeX and epsf.st
The representation type of Ariki-Koike algebras and cyclotomic q-Schur algebras
We give a necessary and sufficient condition on parameters for Ariki-Koike
algebras (resp. cyclotomic q-Schur algebras) to be of finite representation
type.Comment: 23 pages, revised version (correcting some errors, containing some
extended results), to appear in Adv. Mat
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