14,003 research outputs found
Linearization of nonlinear connections on vector and affine bundles, and some applications
A linear connection is associated to a nonlinear connection on a vector
bundle by a linearization procedure. Our definition is intrinsic in terms of
vector fields on the bundle. For a connection on an affine bundle our procedure
can be applied after homogenization and restriction. Several applications in
Classical Mechanics are provided
A Solvable Model for Many Quark Systems in QCD Hamiltonians
Motivated by a canonical, QCD Hamiltonian we propose an effective Hamiltonian
to represent an arbitrary number of quarks in hadronic bags. The structure of
the effective Hamiltonian is discussed and the BCS-type solutions that may
represent constituent quarks are presented. The single particle orbitals are
chosen as 3-dimensional harmonic oscillators and we discuss a class of exact
solutions that can be obtained when a subset of single-particle basis states is
restricted to include a certain number of orbital excitations. The general
problem, which includes all possible orbital states, can also be solved by
combining analytical and numerical methods.Comment: 24 pages, 2 figures, research articl
On the improvement of the low energy neutrino factory
The low energy neutrino factory has been proposed as a very sensitive setup
for future searches for CP violation and matter effects. Here we study how its
performance is affected when the experimental specifications of the setup are
varied. Most notably, we have considered the addition of the 'platinum' nu_{mu}
-> nu_{e} channel. We find that, whilst theoretically the extra channel
provides very useful complementary information and helps to lift degeneracies,
its practical usefulness is lost when considering realistic background levels.
Conversely, an increase in statistics in the 'golden' nu_{e} -> nu_{mu} channel
and, to some extent, an improvement in the energy resolution, lead to an
important increase in the performance of the facility, given the rich energy
dependence of the 'golden' channel at these energies. We show that a low energy
neutrino factory with a baseline of 1300 km, muon energy of 4.5 GeV, and either
a 20 kton totally active scintillating detector or 100 kton liquid argon
detector, can have outstanding sensitivity to the neutrino oscillation
parameters theta13, delta and the mass hierarchy. For our estimated exposure of
2.8 x 10^{23} kton x decays per muon polarity, the low energy neutrino factory
has sensitivity to theta13 and delta for sin^{2}(2theta13) > 10^{-4} and to the
mass hierarchy for sin^{2}(2theta13) > 10^{-3}.Comment: 13 pages, 8 eps figures. Version published in PRD - experimental
section with preliminary results removed, abstract and conclusions re-written
accordingly, title changed, author list amended
Capital social, metas del milenio y desarrollo local : el caso de la Iniciativa de Carapeguá en Desarrollo, Paraguay
¿Puede lo global y lo local generar una sinergia catalizadora del desarrollo comunitario en forma sostenible? ¿Puede la aplicación de la "caja de herramientas" de la gerencia social fortalecer el capital social, que a su vez impulsará el desarrollo local? ¿Puede la capacitación en gerencia social ser un elemento articulador y catalizador del desarrollo local? El objetivo a corto plazo del programa fue el de fortalecer el capital social local para catalizar una estrategia de desarrollo local sostenible, que mejore las condiciones de vida de la población en forma consistente con los objetivos de desarrollo del milenio. Para evaluar el impacto del programa sobre el capital social, se presentan y analizan las acciones y procesos del programa que pudieron haber impactado sobre los distintos elementos que constituyen el acervo de capital social de una comunidad
Cerámica campaniforme de Galicia (NW de España): Caracterización arqueométrica y estudio de procedencia de algunos yacimientos representativos
Se describen los resultados del estudio arqueométrico (composición mineral y elemental) de 55 muestras de recipientes
campaniformes recuperadas en 8 yacimientos arqueológicos del NW de la PenÃnsula Ibérica. Las muestras son representativas
de la variación formal de la cerámica (tanto lisa como decorada) y del tipo de contextos (ceremonial, doméstico
y funerario) donde las cerámicas campaniformes fueron encontradas en la región. Las composiciones mineral y elemental
mostraron un alto grado de coherencia. La mayor parte de los recipientes tenÃa composiciones con proporciones
variables de feldespato potásico y plagioclasa, o de plagioclasa y anfÃbol, coherentes con la litologÃa local. También se
encontraron composiciones mezcla de feldespato potásico y anfÃbol, que no se encuentran de forma natural en los materiales
geológicos del entorno, lo que apunta a una mezcla intencional de materias primas.
La cerámica campaniforme, comparada con la de otros perÃodos previos, muestra fuertes cambios en relación con el estilo,
pero mantiene una continuidad en cuanto al uso de los recursos de materia prima. No se encontró relación entre aspectos
formales y la composición de la cerámica. La mayor parte de la cerámica estudiada procede probablemente del entorno
de los yacimientos. Un análisis de distancias a las áreas potenciales para los materiales, empleando un sistema de
información geográfica, sugiere que prácticamente todas pueden encontrarse en un radio de 16 km (la mayorÃa entre 2 y
5 km), lo que implica una a dos horas. Parece que el esfuerzo asociado a las cerámicas de contextos ceremoniales fue
mayor que el de la cerámica de contextos funerarios y de asentamientoWe describe the results of an archaeometric study (mineral and elemental composition) of 55 samples from Bell Beaker
vessels recovered from 8 archaeological sites in the northwest of the Iberian Peninsula. The samples are representative
of the formal variation of the pottery (both decorated and undecorated) and type of contexts (ceremonial, domestic and
funerary) in which Bell Beaker pottery is found in the region. Both, mineral and elemental composition were found to be
highly consistent. Most of the vessels had compositions resulting from mixtures of potassium feldspar and plagioclase or
plagioclase and amphibole, which are coherent with the local lithology. A few pottery samples showed a mixed composition
of potassium feldspar and amphibole, which is not found naturally in the surrounding geological materials, indicating
an intentional mixing of different raw materials.
Compared to previous periods, Bell Beaker pottery represented a significant change in terms of style but continuity in terms
of the use of raw materials. No relationship was found between the formal aspects and the composition of the pottery. Most
of the samples we studied were probably manufactured with materials obtained from the area around the sites. An analysis
of distances to potential source areas for the materials, using a geographical information system, indicates that almost all
can be found within a radius of 16 km (most between 2-5 km), implying between one and two hours walk. A greater effort
seems to have been associated to pottery of ceremonial sites compared to funerary and settlement sites
Mn valence instability in La2/3Ca1/3MnO3 thin films
A Mn valence instability on La2/3Ca1/3MnO3 thin films, grown on LaAlO3
(001)substrates is observed by x-ray absorption spectroscopy at the Mn L-edge
and O K-edge. As-grown samples, in situ annealed at 800 C in oxygen, exhibit a
Curie temperature well below that of the bulk material. Upon air exposure a
reduction of the saturation magnetization, MS, of the films is detected.
Simultaneously a Mn2+ spectral signature develops, in addition to the expected
Mn3+ and Mn4+ contributions, which increases with time. The similarity of the
spectral results obtained by total electron yield and fluorescence yield
spectroscopy indicates that the location of the Mn valence anomalies is not
confined to a narrow surface region of the film, but can extend throughout the
whole thickness of the sample. High temperature annealing at 1000 C in air,
immediately after growth, improves the magnetic and transport properties of
such films towards the bulk values and the Mn2+ signature in the spectra does
not appear. The Mn valence is then stable even to prolonged air exposure. We
propose a mechanism for the Mn2+ ions formation and discuss the importance of
these observations with respect to previous findings and production of thin
films devices.Comment: Double space, 21 pages, 6 figure
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