14,651 research outputs found
False vacuum decay: effective one-loop action for pair creation of domain walls
An effective one-loop action built from the soliton field itself for the
two-dimensional (2D) problem of soliton pair creation is proposed. The action
consists of the usual mass term and a kinetic term in which the simple
derivative of the soliton field is replaced by a covariant derivative. In this
effective action the soliton charge is treated no longer as a topological
charge but as a Noether charge. Using this effective one-loop action, the
soliton-antisoliton pair production rate is calculated and one recovers Stone's
exponential factor and the prefactor of Kiselev, Selivanov and Voloshin. The
results are also valid straightforwardly to the problem of pair creation rate
of domain walls in dimensions greater than 2.Comment: 12 pages, Late
Half Quantization
A general dynamical system composed by two coupled sectors is considered. The
initial time configuration of one of these sectors is described by a set of
classical data while the other is described by standard quantum data. These
dynamical systems will be named half quantum. The aim of this paper is to
derive the dynamical evolution of a general half quantum system from its full
quantum formulation. The standard approach would be to use quantum mechanics to
make predictions for the time evolution of the half quantum initial data. The
main problem is how can quantum mechanics be applied to a dynamical system
whose initial time configuration is not described by a set of fully quantum
data. A solution to this problem is presented and used, as a guideline to
obtain a general formulation of coupled classical-quantum dynamics. Finally, a
quantization prescription mapping a given classical theory to the correspondent
half quantum one is presented.Comment: 20 pages, LaTex file, Substantially revised versio
Patterns of antenal sensilla of Panstrongylus megistus from three Brazilian states
The objective of the present study was to analyze and describe the phenotype of the antennal sensilla of Panstrongylus megistus, one of the epidemiologically most important species of triatomines in Brazil. Specimens from the Brazilian states of Goiás (GO), Minas Gerais (MG), and Rio Grande do Sul (RS) were compared, based on studies of four types of sensilla on three antennal segments: thick-walled trichoid (TK), thin-walled trichoid (TH), bristles (BR), and basiconica (BA). Discriminant analysis allowed the separation of the RS specimens from those of GO and MG. Multivariate discriminant analysis demonstrated that the sensilla of males differed from those of females, the variables with greatest weight being the BA of all three segments and the TK of flagellum 1. The basiconica sensilla were significantly more abundant in females, on all three segments. Antennal sensilla patterns also demonstrated significant differences among P. megistus specimens.Fil: Villela, M. M.. Fundación Oswaldo Cruz; BrasilFil: Catala, Silvia Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; ArgentinaFil: Juberg, J.. Instituto Oswaldo Cruz; Brasil. Fundación Oswaldo Cruz; BrasilFil: Silva, I. G.. Universidade Federal de Goiás; BrasilFil: Dias, J. C. P.. Fundación Oswaldo Cruz; Brasi
Classical instability of Kerr-AdS black holes and the issue of final state
It is now established that small Kerr-Anti-de Sitter (Kerr-AdS) black holes
are unstable against scalar perturbations, via superradiant amplification
mechanism. We show that small Kerr-AdS black holes are also unstable against
gravitational perturbations and we compute the features of this instability. We
also describe with great detail the evolution of this instability. In
particular, we identify its endpoint state. It corresponds to a Kerr-AdS black
hole whose boundary is an Einstein universe rotating with the light velocity.
This black hole is expected to be slightly oblate and to co-exist in
equilibrium with a certain amount of outside radiation.Comment: 11 pages, RevTex4. v2: small typos corrected. Version to appear in
Phys. Rev.
From OPIMA to MPEG IPMP-X: A standard's history across R&D projects
This paper describes the work performed by a number of companies and universities who have been working as a consortium under the umbrella of the European Union Framework Programme 5 (FP5), Information Society Technologies (IST) research program, in order to provide a set of Digital Rights Management (DRM) technologies and architectures, aiming at helping to reduce the copyright circumvention risks, that have been threatening the music and film industries in their transition from the “analogue” to “digital” age. The paper starts by addressing some of the earlier standardization efforts in the DRM arena, namely, Open Platform Initiative for Multimedia Access (OPIMA). One of the described FP5 IST projects, Open Components for Controlled Access to Multimedia Material (OCCAMM), has developed the OPIMA vision. The paper addresses also the Motion Pictures Expert Group—MPEG DRM work, starting from the MPEG Intellectual Propriety Management and Protection—IPMP “Hooks”, towards the MPEG IPMP Extensions, which has originated the first DRM-related standard (MPEG-4 Part 13, called IPMP Extensions or IPMP-X) ever released by ISO up to the present days.2 The paper clarifies how the FP5 IST project MPEG Open Security for Embedded Systems (MOSES), has extended the OPIMA interfaces and architecture to achieve compliance with the MPEG IPMP-X standard, and how it has contributed to the achievement of “consensus” and to the specification, implementation (Reference Software) and validation (Conformance Testing) of the MPEG IPMP-X standard.info:eu-repo/semantics/acceptedVersio
A QCD sum rule calculation of the decay width
To understand the nature of the , recently observed in the mass
spectrum of the system by the D0 Collaboration, we have
investigated, in a previous work, a scalar tetraquark (diquak-antidiquark)
structure for it, within the two-point QCD sum rules method. The result found
for its mass agrees well with the experimental value. Encouraged by this
finding we now extend our calculations to obtain the decay width of
to using the three-point QCD sum rule. We obtain a value of
(20.4\pm8.7)\MeV, which, on comparing with the experimental value of
21.9\pm6.4 (\mbox{sta})^{+5.0}_{-2.5}(\mbox{syst}) \MeV/c^2, reinforces the
scalar four quark nature of .Comment: Minor modifications made. Some new discussions and references adde
Limiting fragmentation in heavy-ion collisions and percolation of strings
The observed limiting fragmentation of charged particle distributions in
heavy ion collisions is difficult to explain as it does not apply to the proton
spectrum itself. On the other hand, string percolation provides a mechanism to
regenerate fast particles, eventually compensating the rapidity shift (energy
loss) of the nucleons. However a delicate energy-momentum compensation is
required, and in our framework we see no reason for limiting fragmentation to
be exact. A prediction, based on percolation arguments, is given for the
charged particle density in the full rapidity interval at LHC energy .Comment: 9 pages, 2 figures (2 eps files), late
- …