1,013 research outputs found
Calibrating the Na\"ive Cornell Model with NRQCD
Along the years, the Cornell Model has been extraordinarily successful in
describing hadronic phenomenology, in particular in physical situations for
which an effective theory of the strong interactions such as NRQCD cannot be
applied. As a consequence of its achievements, a relevant question is whether
its model parameters can somehow be related to fundamental constants of QCD. We
shall give a first answer in this article by comparing the predictions of both
approaches. Building on results from a previous study on heavy meson
spectroscopy, we calibrate the Cornell model employing NRQCD predictions for
the lowest-lying bottomonium states up to NLO, in which the bottom mass is
varied within a wide range. We find that the Cornell model mass parameter can
be identified, within perturbative uncertainties, with the MSR mass at the
scale GeV. This identification holds for any value of or
the bottom mass, and for all perturbative orders investigated. Furthermore, we
show that: a) the "string tension" parameter is independent of the bottom mass,
and b) the Coulomb strength of the Cornell model can be related to the
QCD strong coupling constant at a characteristic non-relativistic
scale. We also show how to remove the renormalon of the static QCD
potential and sum-up large logs related to the renormalon subtraction by
switching to the low-scale, short-distance MSR mass, and using R-evolution. Our
R-improved expression for the static potential remains independent of the heavy
quark mass value and agrees with lattice QCD results for values of the radius
as large as fm, and with the Cornell model potential at long distances.
Finally we show that for moderate values of , the R-improved NRQCD and
Cornell static potentials are in head-on agreement.Comment: 22 pages, 13 figures, 3 table
Introduction to the Special Issue on Partial Differential Equations and Geometry-Driven Diffusion in Image Processing and Analysis
©1998 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or distribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.DOI: 10.1109/TIP.1998.66117
Superconducting/magnetic three state nanodevice for memory and reading applications
We present a simple nanodevice that can operate in two modes: i) three-state
memory and ii) reading device. The nanodevice is fabricated with an array of
ordered triangular-shaped nanomagnets embedded in a superconducting thin film.
The input signal is ac current and the output signal is dc voltage. Vortex
ratchet effect in combination with out of plane magnetic anisotropy of the
nanomagnets is the background physics which governs the nanodevice performance.Comment: 10 pages, 4 figure
Las interacciones mediáticas de la juventud boliviana: la competencia mediática de jóvenes de La Paz
Se analizan los resultados de una investigación cualitativa en torno a los hábitos de consumo audiovisual y la competencia mediática de la juventud boliviana en la ciudad de La Paz. Los resultados del estudio muestran que la juventud de La Paz consume preferentemente programas televisivos, aunque se extiende con fuerza el uso de Internet, la telefonía móvil y los videojuegos, siendo los medios menos usados la radio y la prensa escrita. A pesar de percibirse como personas críticas, los jóvenes entrevistados muestran carencias en la importancia y necesidad de la educación mediática y de mayor reflexión acerca de los medios
Dispersion Relation Bounds for pi pi Scattering
Axiomatic principles such as analyticity, unitarity and crossing symmetry
constrain the second derivative of the pi pi scattering amplitudes in some
channels to be positive in a region of the Mandelstam plane. Since this region
lies in the domain of validity of chiral perturbation theory, we can use these
positivity conditions to bound linear combinations of \bar{l}_1 and \bar{l}_2.
We compare our predictions with those derived previously in the literature
using similar methods. We compute the one-loop pi pi scattering amplitude in
the linear sigma model (LSM) using the MS-bar scheme, a result hitherto absent
in the literature. The LSM values for \bar{l}_1 and \bar{l}_2 violate the
bounds for small values of m_sigma/m_pi. We show how this can occur, while
still being consistent with the axiomatic principles.Comment: 12 pages, 8 figures. Two references added, a few minor changes.
Published versio
Influenza em suínos no Brasil: o problema e o que pode ser feito para manter a infecção controlada nas granjas afetadas.
Projeto/Plano de Ação: 03.07.05.019
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