862 research outputs found
Infinite-dimensional representations of the rotation group and Dirac's monopole problem
Within the context of infinite-dimensional representations of the rotation
group the Dirac monopole problem is studied in details. Irreducible
infinite-dimensional representations, being realized in the indefinite metric
Hilbert space, are given by linear unbounded operators in infinite-dimensional
topological spaces, supplied with a weak topology and associated weak
convergence. We argue that an arbitrary magnetic charge is allowed, and the
Dirac quantization condition can be replaced by a generalized quantization rule
yielding a new quantum number, the so-called topological spin, which is related
to the weight of the Dirac string.Comment: JHEP style. Extended version of hep-th/0403146. Revised version,
title and some notations are changed. References and Appendix B are adde
The Inverse Scattering Method, Lie-Backlund Transformations and Solitons for Low-energy Effective Field Equations of 5D String Theory
In the framework of the 5D low-energy effective field theory of the heterotic
string with no vector fields excited, we combine two non-linear methods in
order to construct a solitonic field configuration. We first apply the inverse
scattering method on a trivial vacuum solution and obtain an stationary
axisymmetric two-soliton configuration consisting of a massless gravitational
field coupled to a non-trivial chargeless dilaton and to an axion field endowed
with charge. The implementation of this method was done following a scheme
previously proposed by Yurova. We also show that within this scheme, is not
possible to get massive gravitational solitons at all. We then apply a
non-linear Lie-Backlund matrix transformation of Ehlers type on this massless
solution and get a massive rotating axisymmetric gravitational soliton coupled
to axion and dilaton fields endowed with charges. We study as well some
physical properties of the constructed massless and massive solitons and
discuss on the effect of the generalized solution generating technique on the
seed solution and its further generalizations.Comment: 17 pages in latex, changed title, improved text, added reference
Design of a multi-point kinematic coupling for a high precision telescopic simultaneous measurement system
This paper covers the design of a new multi-point kinematic coupling specially developed for a high precision multi-telescopic arm measurement system for the volumetric verification of machine tools with linear and/or rotary axes. The multipoint kinematic coupling allows the simultaneous operation of the three telescopic arms that are registered at the same time to a sphere fixed on the machine tool spindle nose. Every coupling provides an accurate multi-point contact to the sphere, avoiding collisions and interferences with the other two multi-point kinematic couplings, and generating repulsion forces among them to ensure the coupling’s fingers interlacing along the machine tool x/y/z travels in the verification process. Simulation presents minimal deformation of the kinematic coupling under load, assuring the precision of the sphere-to-sphere distance meas-urement. Experimental results are provided to show that the multi-point kinematic coupling developed has repeatability values below ±1.2 µm in the application. © 2021 by the authors. Licensee MDPI, Basel, Switzerland
- Z interferometry at a -factory
We analyze the possibilities that the proposed -factories offer to
measure interference. In the unpolarized beam case, we study
different signatures in the channel, taking advantage of the
presence of the near-by resonance. We build a C-odd forward-backward
asymmetry, estimated to be around , and (P-even, T-even) and (P-odd,
T-odd) alignments of the , to be seen from the angular distribution of
its decay products. With polarized electrons a left-right asymmetry
around is present in all channels. At leading order this
asymmetry is independent of hadronic matrix elements and is sensitive to the
vector coupling. In the channel, a combined
left-right forward-backward asymmetry is considered.Comment: 29 pages + 6 figures. Some changes concerning observables,
especially related with possible 2 contribution
Metabolic syndrome before puberty: Myth or reality?
Metabolic syndrome (MetS) is defined as a cluster of alterations related with insulin resistance (obesity, dyslipidemia, hypertension, and impaired glucose metabolism), which are associated with a higher risk of cardiovascular disease in adults. Several definitions have been proposed for older children and adolescents. However, no definitions have been made in accordance with pubertal status, and those in prepubertal state have not received attention enough, despite there are data suggesting the early presence of risk factors. The new insights concerning healthy and unhealthy metabolic status or the addition of novel metabolic risk biomarkers, may contribute to the knowledge about the development of MetS in children. This manuscript reviews the available evidence on MetS during childhood, focusing on the prepubertal period
CP--Violating Invariants in Supersymmetry
I study the weak basis CP-violating invariants in supersymmetric models, in
particular those which cannot be expressed in terms of the Jarlskog--type
invariants, and find basis--independent conditions for CP conservation. With an
example of the K-anti-K mixing, I clarify what are the combinations of
supersymmetric parameters which are constrained by experiment.Comment: matches the PRD versio
3D heterotic string theory: new approach and extremal solutions
We develop a new formalism for the bosonic sector of low-energy heterotic
string theory toroidally compactified to three dimensions. This formalism is
based on the use of some single non-quadratic real matrix potential which
transforms linearly under the action of subgroup of the three-dimensional
charging symmetries. We formulate a new charging symmetry invariant approach
for the symmetry generation and straightforward construction of asymptotically
flat solutions. Finally, using the developed approach and the established
formal analogy between the heterotic and Einstein-Maxwell theories, we
construct a general class of the heterotic string theory extremal solutions of
the Israel-Wilson-Perjes type. This class is asymptotically flat and charging
symmetry complete; it includes the extremal solutions constructed before and
possesses the non-trivial bosonic string theory limit.Comment: 20 pages in Late
Remote sensing for greenhouse detection from stereo pairs of WorldView-2 satellite
Revista oficial de la Asociación Española de Teledetección[EN] The successful launch of the first very high resolution (VHR) satellites capable of capturing panchromatic imagery of the land surface with ground sample distance even lower than 1 m (e.g. IKONOS in 1999 or QuickBird in 2001) marked the beginning of a wholly new age in remote sensing. On January 4, 2010, images of WorldView-2 were placed on the market. Possibly it is the most sophisticated commercial VHR satellite currently orbiting the Earth and the exploitation of its data poses a challenge to researchers worldwide. Moreover, the practice of under plastic agriculture had a great development in the Mediterranean area during the past 60 years, especially in Almeria, acting as a key economic driver in the area. The goal of this work is the automatic greenhouse mapping by using Object Based Image Analysis (OBIA). The required input data will be a pan-sharpened orthoimage and a normalized digital surface model (nDSM) for objects, both products generated from a WorldView-2 stereo pair. The attained results show that the very high resolution 8-band multispectral and the nDSM data improve the greenhouses automatic detection. In this way, overall accuracies higher than 90% can be achieved.[ES] El 4 de enero de 2010, se comenzaron a comercializar imágenes del satélite comercial de muy alta resolución (Very High Resolution; VHR) más sofisticado que actualmente orbita sobre la tierra. Se trata de WorldView-2, cuya resolución tanto geométrica (0.46 m y 1.84 m de tamaño de pixel en el nadir en la imagen pancromática y en la multiespectral respectivamente) como espectral (es el único satélite comercial VHR con 8 bandas en su imagen multiespectral) hacen que la explotación de sus datos suponga un verdadero desafío para investigadores de todo el mundo. Por otra parte, la práctica de la agricultura bajo plástico ha tenido un gran desarrollo en el área Mediterránea durante los últimos 60 años, especialmente en Almería, suponiendo un motor económico fundamental en la zona. El objetivo de este trabajo es la detección de invernaderos aplicando técnicas de análisis de imágenes basadas en objetos (OBIA). La información de base consistirá en una ortoimagen fusionada y datos de elevaciones de objetos, ambos productos obtenidos a partir de un estéreo par de imágenes del satélite de muy alta resolución WorldView-2. Los resultados obtenidos indican que el uso de las ocho bandas multiespectrales, junto a la inclusión de datos altimétricos mejoran las precisiones en la clasificación de invernaderos, pudiéndose obtener precisiones globales superiores al 90%.Este trabajo se ha desarrollado en el marco de los Proyecto del Plan Nacional de Investigación con referencias CTM2010-16573 y AGL2013- 42603-R, financiados por el Ministerio de Ciencia e Innovación del Gobierno de España y con fondos
FEDER. El trabajo ha sido también cofinanciado mediante fondos FEDER a través del Programa de Cooperación Transfronteriza España-Fronteras Exteriores, POCTEFEX 2008-2013 (referencia 0065_COPTRUST_3_E). Los autores agradecen el apoyo de la Junta de Andalucía a través del Proyecto de Excelencia RNM-3575 y al Campus de Excelencia Internacional Agroalimentario ceiA3 (http://www.ceia3.es/).Aguilar, M.; Montalbán, M.; Saldaña, M.; Aguilar, F.; Fernández, I.; García-Lorca, A. (2014). Detección remota de invernaderos a partir de estéreo pares del satélite WorldView-2. Revista de Teledetección. (41):19-28. https://doi.org/10.4995/raet.2014.2288SWORD192841Espí, E., Salmerón, A., Fontecha, A., García, Y., & Real, A. I. (2006). PLastic Films for Agricultural Applications. Journal of Plastic Film & Sheeting, 22(2), 85-102. doi:10.1177/8756087906064220FAO, 2002. El cultivo protegido en clima mediterráneo. Estudio FAO Producción y Protección Vegetal 90, Organización de las Naciones Unidas para la Agricultura y la Alimentación, Roma.Torrens, M., 2006. El sector de Invernaderos en Marruecos. Instituto Espa-ol de Comercio Exterior (ICEX). Nota Sectorial, 15 pp
Solution of coupled vertex and propagator Dyson-Schwinger equations in the scalar Munczek-Nemirovsky model
In a scalar model, we exactly solve the vertex and
propagator Dyson-Schwinger equations under the assumption of a spatially
constant (Munczek-Nemirovsky) propagator for the field. Various
truncation schemes are also considered.Comment: 7 pages,4 figures, minor changes, reference added for published
versio
The quadratic scalar radius of the pion and the mixed radius
We consider the quadratic scalar radius of the pion, ,
and the mixed $K-\pi$ scalar radius, . With respect to
the second, we point out that the more recent (post-1974) experimental results
in decays imply a value, , which is about above estimates based on chiral perturbation
theory. On the other hand, we show that this value of
suggests the existence of a low mass S$\tfrac{1}{2}$ $K\pi$ resonance. With
respect to , we contest the central value and accuracy of
current evaluations, that give .
Based on experiment, we find a robust lower bound of and a reliable estimate, , where the error bars are attainable. This
implies, in particular, that the chiral result for is
away from experiment. We also comment on implications about the
chiral parameter , very likely substantially larger (and with larger
errors) than usually assumed.Comment: PlainTeX file. Corrected asymptotic phase; numerical results
unaffecte
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