9,331 research outputs found
Relative Asymptotic of Multiple Orthogonal Polynomials for Nikishin Systems
We prove relative asymptotic for the ratio of two sequences of multiple
orthogonal polynomials with respect to Nikishin system of measures. The first
Nikishin system is such that for each
, has constant sign on its compact support \supp {\sigma_k}
\subset \mathbb{R} consisting of an interval , on which
almost everywhere, and a discrete set without
accumulation points in . If
{Co}(\supp {\sigma_k}) = \Delta_k denotes the smallest interval containing
\supp {\sigma_k}, we assume that ,
. The second Nikishin system
is a perturbation of the first by
means of rational functions , whose zeros and poles lie in
.Comment: 30 page
Rotating and counterrotating relativistic thin disks as sources of stationary electrovacuum spacetimes
A detailed study is presented of the counterrotating model (CRM) for
electrovacuum stationary axially symmetric relativistic thin disks of infinite
extension without radial stress, in the case when the eigenvalues of the
energy-momentum tensor of the disk are real quantities, so that there is not
heat flow. We find a general constraint over the counterrotating tangential
velocities needed to cast the surface energy-momentum tensor of the disk as the
superposition of two counterrotating charged dust fluids. We then show that, in
some cases, this constraint can be satisfied if we take the two counterrotating
tangential velocities as equal and opposite or by taking the two
counterrotating streams as circulating along electro-geodesics. However, we
show that, in general, it is not possible to take the two counterrotating
fluids as circulating along electro-geodesics nor take the two counterrotating
tangential velocities as equal and opposite. A simple family of models of
counterrotating charged disks based on the Kerr-Newman solution are considered
where we obtain some disks with a CRM well behaved. We also show that the disks
constructed from the Kerr-Newman solution can be interpreted, for all the
values of parameters, as a matter distribution with currents and purely
azimuthal pressure without heat flow. The models are constructed using the
well-known "displace, cut and reflect" method extended to solutions of vacuum
Einstein-Maxwell equations. We obtain, in all the cases, counterrotating
Kerr-Newman disks that are in agreement with all the energy conditions.Comment: 22 pages, 7 figures, Late
The Martin-Benito-Mena Marugan-Olmedo prescription for the Dapor-Liegener model of Loop Quantum Cosmology
Recently, an alternative Hamiltonian constraint for Loop Quantum Cosmology
has been put forward by Dapor and Liegener, inspired by previous work on
regularization due to Thiemann. Here, we quantize this Hamiltonian following a
prescription for cosmology proposed by Mart\'{\i}n-Benito, Mena Marug\'an, and
Olmedo. To this effect, we first regularize the Euclidean and Lorentzian parts
of the Hamiltonian constraint separately in the case of a Bianchi I cosmology.
This allows us to identify a natural symmetrization of the Hamiltonian which is
apparent in anisotropic scenarios. Preserving this symmetrization in isotropic
regimes, we then determine the Hamiltonian constraint corresponding to a
Friedmann-Lema\^itre-Robertson-Walker cosmology, which we proceed to quantize.
We compute the action of this Hamiltonian operator in the volume eigenbasis and
show that it takes the form of a fourth-order difference equation, unlike in
standard Loop Quantum Cosmology, where it is known to be of second order. We
investigate the superselection sectors of our constraint operator, proving that
they are semilattices supported only on either the positive or the negative
semiaxis, depending on the triad orientation. Remarkably, the decoupling
between semiaxes allows us to write a closed expression for the generalized
eigenfunctions of the geometric part of the constraint. This expression is
totally determined by the values at the two points of the semilattice that are
closest to the origin, namely the two contributions with smallest eigenvolume.
This is in clear contrast with the situation found for the standard Hamiltonian
of Loop Quantum Cosmology, where only the smallest value is free. This result
indicates that the degeneracy of the new geometric Hamiltonian operator is
equal to two, doubling the possible number of solutions with respect to the
conventional quantization considered until now.Comment: 15 pages, published in Physical Review
Alternative Multiple Spanning Tree Protocol (AMSTP) for Optical Ethernet Backbones
The availability and affordable cost of Gigabit and 10 Gigabit Ethernet switches has impacted the deployment of metropolitan area networks (MAN) and campus networks. This paper presents a new protocol, the alternative multiple spanning tree protocol (AMSTP), that uses multiple source based spanning trees for backbones using Ethernet switches. It provides minimum paths and more efficient usage of optical backbone infrastructure than currently proposed protocols such as resilient packet ring and rapid spanning tree. The protocol exhibits features similar to MAC routing protocols like Link State Over MAC (LSOM) such as optimum path and effective infrastructure usage, without requiring MAC routing due to the use of the spanning tree protocol paradigm. AMSTP is not restricted to specific topologies such as ring or tree, but performs efficiently in arbitrary topologies. Among the application areas are optical backbones of campus and MANs.Publicad
Inclusive Development in Latin America and Smallholders’ Interactive Learning Spaces
Inclusive development appears as a challenge in Latin America countries after the rupture of the social inclusion as a trickle-down effect of the economic growth. Searching development with inclusion several public policies were implemented in Latin American focusing in the agri-food production. In order to assess the progress to reach such objectives, two cases are studied. Smallholder milk producers at the Loma Blanca community (Mexico) and smallholders olive producers at Aimogasta (Argentina) were considered. Interactive learning spaces were clearly identified as consequence of the linking between product, producers and territory. Despite these results, several queries are still opened.Fil: Bastida Mercado, Claudia. Universidad Autónoma del Estado de México; MéxicoFil: García Martínez, Anastacio. Universidad Autónoma del Estado de México; MéxicoFil: Sanchez, Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Centro de Estudios Urbanos y Regionales; Argentina. Universidad de Morón; Argentina. Instituto Nacional de Tecnología Agropecuaria; Argentin
Del monumento al paisaje urbano
Las intervenciones del Palacio Municipal, la Iglesia La Merced y la Estación Ferroviaria significan hechos importantes en el contexto histórico de la Ensenada y quizá el inicio de un programa de recuperación del rico patrimonio local marcado por acontecimientos de indudable valor para la memoria de los argentinos.
El histórico edificio Municipal frente a la plaza principal de la localidad, calles La Merced esquina Don Bosco, significó el eslabón inicial del “Programa Preservación de Obras Públicas de Valor Histórico”. La Iglesia sobre la misma plaza Belgrano el siguiente eslabón.
El crecimiento de Ensenada se apoyó en la llegada del ferrocarril. La Antigua Estación de trenes, que había alcanzado tal nivel de deterioro y abandono; es hoy también recuperada por la Municipalidad de Ensenada. Los tres edificios son parte de un proceso de renovación urbana, destinado a recuperar monumentos para disfrute y uso de la ciudadanía
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