1,563 research outputs found
A Survey of Star Product Geometry
A brief pedagogical survey of the star product is provided, through
Groenewold's original construction based on the Weyl correspondence. It is then
illustrated how simple Landau orbits in a constant magnetic field, through
their Dirac Brackets, define a noncommutative structure since these brackets
exponentiate to a star product---a circumstance rarely operative for generic
Dirac Brackets. The geometric picture of the star product based on its Fourier
representation kernel is utilized in the evaluation of chains of star products.
The intuitive appreciation of their associativity and symmetries is thereby
enhanced. This construction is compared and contrasted with the remarkable
phase-space polygon construction of Almeida.Comment: 14p, LateX/crckapb.sty, proceedings of NATO ARW: UIC 2000, July 22-2
Branes, Quantum Nambu Brackets, and the Hydrogen Atom
The Nambu Bracket quantization of the Hydrogen atom is worked out as an
illustration of the general method. The dynamics of topological open branes is
controlled classically by Nambu Brackets. Such branes then may be quantized
through the consistent quantization of the underlying Nambu brackets: properly
defined, the Quantum Nambu Brackets comprise an associative structure, although
the naive derivation property is mooted through operator entwinement. For
superintegrable systems, such as the Hydrogen atom, the results coincide with
those furnished by Hamiltonian quantization--but the method is not limited to
Hamiltonian systems.Comment: 6 pages, LateX2e. Invited talk by CZ at the XIII International
Colloquium on Integrable Systems and Quantum Groups, Prague, June 18, 200
Recommended from our members
Motion estimation with object based regularisation
A dynamic programming based matching method for motion estimation, that optimises a Bayesian maximum likelihood function in a 3-D optimisation space, is presented. The Bayesian function consists of a matching cost and an object based 2-D regularisation cost. The method gives results more accurate than block-based matching since the motion boundaries are close to the actual object boundaries
Semi-automated creation of converged iTV services: From macromedia director simulations to services ready for broadcast
While sound and video may capture viewers’ attention, interaction can captivate them. This has not been available prior to the advent of Digital Television. In fact, what lies at the heart of the Digital Television revolution
is this new type of interactive content, offered
in the form of interactive Television (iTV) services. On top of that, the new world of converged networks has created a demand for a new type of converged services on a range of mobile terminals (Tablet PCs, PDAs and mobile phones). This paper aims at presenting a new approach to service creation that allows for the semi-automatic translation of simulations and rapid prototypes created in the accessible desktop
multimedia authoring package Macromedia Director
into services ready for broadcast. This is achieved by a series of tools that de-skill and speed-up the process of creating digital TV user interfaces (UI) and applications for mobile terminals.
The benefits of rapid prototyping are essential for the production of these new types of services, and are therefore discussed in the first section of this paper.
In the following sections, an overview of the
operation of content, service, creation and management sub-systems is presented, which illustrates why these tools compose an important and integral part of a system responsible of creating, delivering and managing converged broadcast and telecommunications services.
The next section examines a number of metadata
languages candidates for describing the iTV services user interface and the schema language adopted in this project. A detailed description of the operation of the two tools is provided to offer an insight of how they can be used to de-skill and speed-up the process of creating digital TV user interfaces and applications for mobile terminals. Finally, representative broadcast oriented and telecommunication oriented converged service components are also introduced, demonstrating how these tools have been used to generate different types of services
Semileptonic B Decays at BABAR
We present results on semileptonic B decays obtained with the BABAR detector.
The large data set accumulated at the PEP-II asymmetric-energy B-Factory allows
a new measurement technique, where the hadronic decay of one B meson is fully
reconstructed and the semileptonic decay of the recoiling B meson is studied.
Traditional analysis techniques of inclusive and exclusive B decays complement
this approach with very high statistics data samples. These measurements play
an important role in the tests of the description of CP violation in the
Standard Model: The determinations of the Cabibbo-Kobayashi-Maskawa matrix
elements |Vcb| and |Vub| provide constraints on the unitarity of the CKM
triangle. Furthermore, the experimental measurement of parameters of Heavy
Quark Effective Theory test the consistency of the theoretical description of
semileptonic B decays.Comment: Invited Brief Review, to appear in Modern Physics Letters
Revitalising African agriculture through innovative business models and organisational arrangements : promising developments in the traditional crops sector.
Within the last four years, a number of high profile reports outlining new strategies for pulling African agriculture out of its current impasse have emerged. These include the Comprehensive African Agriculture Development Programme of NEPAD, and the InterAcademy Council Report commissioned by UN Secretary General Koffi Annan. Whilst these strategies are a welcome improvement on those that have characterised African agriculture in the past, it is argued here that like their predecessors, they fail to focus on business-competitive approaches as an integral part of the reform package needed to stimulate African agricultural productivity and development. This paper draws on innovation, business and organisation literature to highlight some of these approaches. It focuses on three concepts : value innovation, lead user focus and organisational value logic
Phase-space Quantization of Field Theory
In this lecture, a limited introduction of gauge invariance in phase-space is
provided, predicated on canonical transformations in quantum phase-space. Exact
characteristic trajectories are also specified for the time-propagating Wigner
phase-space distribution function: they are especially simple - indeed,
classical - for the quantized simple harmonic oscillator. This serves as the
underpinning of the field theoretic Wigner functional formulation introduced.
Scalar field theory is thus reformulated in terms of distributions in field
phase-space. This is a pedagogical selection from work published in J Phys A32
(1999) 771 and Phys Rev D58 (1998) 025002, reported at the Yukawa Institute
Workshop "Gauge Theory and Integrable Models", 26-29 January, 1999.Comment: 14 pages, LaTeX, 1 eps figure, epsf.sty, ptptex.sty, ptp-text.sty
Reported at the YITP Workshop "Gauge Theory and Integrable Models", 26-29
January, 1999. References added and graphics update
Deformation Quantization of Nambu Mechanics
Phase Space is the framework best suited for quantizing superintegrable
systems--systems with more conserved quantities than degrees of freedom. In
this quantization method, the symmetry algebras of the hamiltonian invariants
are preserved most naturally, as illustrated on nonlinear -models,
specifically for Chiral Models and de Sitter -spheres. Classically, the
dynamics of superintegrable models such as these is automatically also
described by Nambu Brackets involving the extra symmetry invariants of them.
The phase-space quantization worked out then leads to the quantization of the
corresponding Nambu Brackets, validating Nambu's original proposal, despite
excessive fears of inconsistency which have arisen over the years. This is a
pedagogical talk based on hep-th/0205063 and hep-th/0212267, stressing points
of interpretation and care needed in appreciating the consistency of Quantum
Nambu Brackets in phase space. For a parallel discussion in Hilbert space, see
T Curtright's contribution in these Proceedings [hep-th 0303088].Comment: Invited talk by the first author at the Coral Gables Conference
(C02/12/11.2), Ft Lauderdale, Dec 2002. 14p, LateX2e, aipproc, amsfont
Enabling error-resilient internet broadcasting using motion compensated spatial partitioning and packet FEC for the dirac video codec
Video transmission over the wireless or wired
network require protection from channel errors since compressed video bitstreams are very sensitive to transmission errors because of the use of predictive coding and variable length coding. In this paper, a simple, low complexity and patent free error-resilient coding is proposed. It is based upon the idea of using spatial partitioning on the motion compensated residual frame without employing the transform coefficient coding. The proposed scheme is intended for open source Dirac video codec in order to enable the codec to be used for Internet
broadcasting. By partitioning the wavelet transform coefficients of the motion compensated residual frame into groups and independently processing each group using arithmetic coding and Forward Error Correction (FEC), robustness to transmission errors over the packet erasure
wired network could be achieved. Using the Rate
Compatibles Punctured Code (RCPC) and Turbo Code
(TC) as the FEC, the proposed technique provides
gracefully decreasing perceptual quality over packet loss rates up to 30%. The PSNR performance is much better when compared with the conventional data partitioning only methods. Simulation results show that the use of multiple
partitioning of wavelet coefficient in Dirac can achieve up to 8 dB PSNR gain over its existing un-partitioned method
- …