1,535 research outputs found
Integrable Quantum Field Theories with Unstable Particles
A new family of S-matrix theories with resonance poles is constructed and
conjectured to correspond to the Homogeneous sine-Gordon theories associated
with simply laced compact Lie groups, where some of the resonance poles can be
traced to the presence of unstable particles in the spectrum. These theories
are unitary in the usual S S^\dagger =1 sense, they are not parity invariant,
and they exhibit continuous coupling constants that determine both the mass
spectrum of stable particles and the masses and the position of the resonance
poles.Comment: One reference added, 12 pages, LaTeX fil
Hermitian analyticity versus Real analyticity in two-dimensional factorised S-matrix theories
The constraints implied by analyticity in two-dimensional factorised S-matrix
theories are reviewed. Whenever the theory is not time-reversal invariant, it
is argued that the familiar condition of `Real analyticity' for the S-matrix
amplitudes has to be superseded by a different one known as `Hermitian
analyticity'. Examples are provided of integrable quantum field theories whose
(diagonal) two-particle S-matrix amplitudes are Hermitian analytic but not Real
analytic. It is also shown that Hermitian analyticity is consistent with the
bootstrap equations and that it ensures the equivalence between the notion of
unitarity in the quantum group approach to factorised S-matrices and the
genuine unitarity of the S-matrix.Comment: 9 pages, LaTeX file. The comments about unitarity in affine Toda
theories have been improved. The basis dependence of the Hermitian
analyticity conditions is discusse
Quantum Modelling of Electro-Optic Modulators
Many components that are employed in quantum information and communication
systems are well known photonic devices encountered in standard optical fiber
communication systems, such as optical beamsplitters, waveguide couplers and
junctions, electro-optic modulators and optical fiber links. The use of these
photonic devices is becoming increasingly important especially in the context
of their possible integration either in a specifically designed system or in an
already deployed end-to-end fiber link. Whereas the behavior of these devices
is well known under the classical regime, in some cases their operation under
quantum conditions is less well understood. This paper reviews the salient
features of the quantum scattering theory describing both the operation of the
electro-optic phase and amplitude modulators in discrete and continuous-mode
formalisms. This subject is timely and of importance in light of the increasing
utilization of these devices in a variety of systems, including quantum key
distribution and single-photon wavepacket measurement and conformation. In
addition, the paper includes a tutorial development of the use of these models
in selected but yet important applications, such as single and multi-tone
modulation of photons, two-photon interference with phase-modulated light or
the description of amplitude modulation as a quantum operation.Comment: 29 pages, 10 figures, Laser and Photonics Reviews (in press
The Hamiltonian Structure of Soliton Equations and Deformed W-Algebras
The Poisson bracket algebra corresponding to the second Hamiltonian structure
of a large class of generalized KdV and mKdV integrable hierarchies is
carefully analysed. These algebras are known to have conformal properties, and
their relation to -algebras has been previously investigated in some
particular cases. The class of equations that is considered includes
practically all the generalizations of the Drinfel'd-Sokolov hierarchies
constructed in the literature. In particular, it has been recently shown that
it includes matrix generalizations of the Gelfand-Dickey and the constrained KP
hierarchies. Therefore, our results provide a unified description of the
relation between the Hamiltonian structure of soliton equations and -algebras, and it comprises almost all the results formerly obtained by other
authors. The main result of this paper is an explicit general equation showing
that the second Poisson bracket algebra is a deformation of the Dirac bracket
algebra corresponding to the -algebras obtained through Hamiltonian
reduction.Comment: 41 pages, plain TeX, no figures. New introduction and references
added. Version to be published in Annals of Physics (N.Y.
Semi-classical spectrum of the Homogeneous sine-Gordon theories
The semi-classical spectrum of the Homogeneous sine-Gordon theories
associated with an arbitrary compact simple Lie group G is obtained and shown
to be entirely given by solitons. These theories describe quantum integrable
massive perturbations of Gepner's G-parafermions whose classical
equations-of-motion are non-abelian affine Toda equations. One-soliton
solutions are constructed by embeddings of the SU(2) complex sine-Gordon
soliton in the regular SU(2) subgroups of G. The resulting spectrum exhibits
both stable and unstable particles, which is a peculiar feature shared with the
spectrum of monopoles and dyons in N=2 and N=4 supersymmetric gauge theories.Comment: 28 pages, plain TeX, no figure
The platforms and the creation of mainstream contents: An approach to the new ‘convergent fictions
Las plataformas de contenidos audiovisuales se han convertido en los agentes fundamentales
de la nueva configuración de la industria internacional (y en algunos casos, local), modificando
hábitos de consumo a través no solo de la compra y difusión de los productos de sus catálogos,
sino también con la producción propia de contenidos. Sin pretender ahondar en un análisis
exhaustivo del mercado ni tampoco en los comportamientos del consumidor contemporáneo,
el objetivo del presente artículo es entender cómo los cambios tecnológicos y estructurales
generados a partir de la llegada de Internet y el uso mayoritario del streaming han podido
repercutir en la narrativa, estética e ideología de los actuales productos televisivos y cinematográficos
que, sin formar una tipología específica, albergan unas características que nos permiten
agruparlos bajo los parámetros del mainstream y acercándonos a la categoría y definición
de «ficciones convergentes»Audiovisual content platforms have become the main players of today’s international (and in
some cases local) industry changing consumption habits not only through the purchase and difussion
of their products, but also through the production of their own content. The main goal of
this article is to understand how these audiovisual and structural changes propagated by the Internet
and a wider use of streaming could have determined the narrative, aesthetic and ideology
of current television and cinematic products. However, I do not intend to present an exhaustive
analysis of the audiovisual sector nor of the contemporary consumer’s behauviour. Even though
these works do not belong to a specific typology, they have similar features that allow us to classify
them according to the parameters of mainstream products and close the gap with a new
category and definition, the ‘convergent fictions
Optimization of throughput, fairness and energy efficiency on asymmetric multicore systems via OS scheduling
Most of chip multiprocessors (CMPs) are symmetric, i.e. they are composed of identical cores. These CMPs may consist of complex cores (e.g., Intel Haswell or IBM Power8) or simple and lower-power cores (e.g. ARM Cortex A9 or Intel Xeon Phi). Cores in the former approach have advanced microarchitectural features, such as out-of-order super-scalar pipelines, and they are suitable for running sequential applications which use them efficiently. Cores in the latter approach have a simple microarchitecture and are good for running applications with high thread-level parallelism (TLP).Facultad de Informátic
Optimization of throughput, fairness and energy efficiency on asymmetric multicore systems via OS scheduling
Most of chip multiprocessors (CMPs) are symmetric, i.e. they are composed of identical cores. These CMPs may consist of complex cores (e.g., Intel Haswell or IBM Power8) or simple and lower-power cores (e.g. ARM Cortex A9 or Intel Xeon Phi). Cores in the former approach have advanced microarchitectural features, such as out-of-order super-scalar pipelines, and they are suitable for running sequential applications which use them efficiently. Cores in the latter approach have a simple microarchitecture and are good for running applications with high thread-level parallelism (TLP).Facultad de Informátic
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