6,701 research outputs found
Representation theory of the higher order peak algebras
The representation theory (idempotents, quivers, Cartan invariants and Loewy
series) of the higher order unital peak algebras is investigated. On the way,
we obtain new interpretations and generating functions for the idempotents of
descent algebras introduced in [F. Saliola, J. Algebra 320 (2008) 3866.]Comment: 30 page
Metrics and causality on Moyal planes
Metrics structures stemming from the Connes distance promote Moyal planes to
the status of quantum metric spaces. We discuss this aspect in the light of
recent developments, emphasizing the role of Moyal planes as representative
examples of a recently introduced notion of quantum (noncommutative) locally
compact space. We move then to the framework of Lorentzian noncommutative
geometry and we examine the possibility of defining a notion of causality on
Moyal plane, which is somewhat controversial in the area of mathematical
physics. We show the actual existence of causal relations between the elements
of a particular class of pure (coherent) states on Moyal plane with related
causal structure similar to the one of the usual Minkowski space, up to the
notion of locality.Comment: 33 pages. Improved version; a summary added at the end of the
introduction, misprints corrected. Version to appear in Contemporary
Mathematic
QuickCSG: Fast Arbitrary Boolean Combinations of N Solids
QuickCSG computes the result for general N-polyhedron boolean expressions
without an intermediate tree of solids. We propose a vertex-centric view of the
problem, which simplifies the identification of final geometric contributions,
and facilitates its spatial decomposition. The problem is then cast in a single
KD-tree exploration, geared toward the result by early pruning of any region of
space not contributing to the final surface. We assume strong regularity
properties on the input meshes and that they are in general position. This
simplifying assumption, in combination with our vertex-centric approach,
improves the speed of the approach. Complemented with a task-stealing
parallelization, the algorithm achieves breakthrough performance, one to two
orders of magnitude speedups with respect to state-of-the-art CPU algorithms,
on boolean operations over two to dozens of polyhedra. The algorithm also
outperforms GPU implementations with approximate discretizations, while
producing an output without redundant facets. Despite the restrictive
assumptions on the input, we show the usefulness of QuickCSG for applications
with large CSG problems and strong temporal constraints, e.g. modeling for 3D
printers, reconstruction from visual hulls and collision detection
Properties of Cosmological Filaments extracted from Eulerian Simulations
Using a new parallel algorithm implemented within the VisIt framework, we
analysed large cosmological grid simulations to study the properties of baryons
in filaments. The procedure allows us to build large catalogues with up to
filaments per simulated volume and to investigate the
properties of cosmic filaments for very large volumes at high resolution (up to
simulated with cells). We determined scaling
relations for the mass, volume, length and temperature of filaments and
compared them to those of galaxy clusters. The longest filaments have a total
length of about with a mass of several . We
also investigated the effects of different gas physics. Radiative cooling
significantly modifies the thermal properties of the warm-hot-intergalactic
medium of filaments, mainly by lowering their mean temperature via line
cooling. On the other hand, powerful feedback from active galactic nuclei in
surrounding halos can heat up the gas in filaments. The impact of
shock-accelerated cosmic rays from diffusive shock acceleration on filaments is
small and the ratio of between cosmic ray and gas pressure within filaments is
of the order of percent.Comment: 27 pages, 24 figures, accepted for publication in Monthly Notices of
the Royal Astronomical Society Main Journa
Chromomagnetism, flavour symmetry breaking and S-wave tetraquarks
The chromomagnetic interaction, with full account for flavour-symmetry
breaking, is applied to S-wave configurations containing two quarks and two
antiquarks. Phenomenological implications are discussed for light, charmed,
charmed and strange, hidden-charm and double-charm mesons, and extended to
their analogues with beauty.Comment: 16 pages, 2 figures, RevTeX, Refs. updated, further typos corrected,
to appear in EPJ
QuickCSG: Fast Arbitrary Boolean Combinations of N Solids
QuickCSG computes the result for general N-polyhedron boolean expressions
without an intermediate tree of solids. We propose a vertex-centric view of the
problem, which simplifies the identification of final geometric contributions,
and facilitates its spatial decomposition. The problem is then cast in a single
KD-tree exploration, geared toward the result by early pruning of any region of
space not contributing to the final surface. We assume strong regularity
properties on the input meshes and that they are in general position. This
simplifying assumption, in combination with our vertex-centric approach,
improves the speed of the approach. Complemented with a task-stealing
parallelization, the algorithm achieves breakthrough performance, one to two
orders of magnitude speedups with respect to state-of-the-art CPU algorithms,
on boolean operations over two to dozens of polyhedra. The algorithm also
outperforms GPU implementations with approximate discretizations, while
producing an output without redundant facets. Despite the restrictive
assumptions on the input, we show the usefulness of QuickCSG for applications
with large CSG problems and strong temporal constraints, e.g. modeling for 3D
printers, reconstruction from visual hulls and collision detection
Introduction
Introduction to the special issue
Pastiche in Contemporary Latin American Literature
Pastiche, defined as non-satiric imitation, is a characteristic feature of contemporary Latin American narrative. Although unlike parody it does not stand in antagonist relationship with a prior text, nevertheless pastiche marks a distance and a displacement of other texts. The article illustrates this with reference to Mario Vargas Llosa\u27s pastiche of Machiguenga indigenous legends in his novel El hablador and Silviano Santiago\u27s pastiche of Graciliano Ramos\u27s prison memories in his novel, Em Liberdade
Shape Animation with Combined Captured and Simulated Dynamics
We present a novel volumetric animation generation framework to create new
types of animations from raw 3D surface or point cloud sequence of captured
real performances. The framework considers as input time incoherent 3D
observations of a moving shape, and is thus particularly suitable for the
output of performance capture platforms. In our system, a suitable virtual
representation of the actor is built from real captures that allows seamless
combination and simulation with virtual external forces and objects, in which
the original captured actor can be reshaped, disassembled or reassembled from
user-specified virtual physics. Instead of using the dominant surface-based
geometric representation of the capture, which is less suitable for volumetric
effects, our pipeline exploits Centroidal Voronoi tessellation decompositions
as unified volumetric representation of the real captured actor, which we show
can be used seamlessly as a building block for all processing stages, from
capture and tracking to virtual physic simulation. The representation makes no
human specific assumption and can be used to capture and re-simulate the actor
with props or other moving scenery elements. We demonstrate the potential of
this pipeline for virtual reanimation of a real captured event with various
unprecedented volumetric visual effects, such as volumetric distortion,
erosion, morphing, gravity pull, or collisions
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