Performance Analysis of Throughput Efficient Switch-over between FSO and mmW Links

Free Space Optics (FSO) links provide usage of high bandwidth and the flexibility of wireless communication links. However, weather patterns like fog and heavy snow fall limit the availability of FSO. Another technology providing similar properties regarding offered data rates and flexibility of setup is Millimeter Wave Technology (mmW), operating at several tens of GHz. In this case, heavy rain limits mmW link availability. A combination of both technologies had been proved to be very effective to achieve very high availability. Different hybrid architectures of these two links and switch-over techniques had been proposed in the recent years. All of these techniques require redundant transmission on either both transmission links or waste bandwidth of backup link when main FSO link is operational. In this paper, a switch-over between these technologies is proposed, to maintain high availability without the loss of transmission bandwidth. The performance of this switch-over has been simulated for more than one year measured availability data for hybrid network of mmW link and FSO link. The switch over behavior has also been simulated for fog, rain and snow events. It has been shown that the availability with switch-over reaches the redundant link availability but switchover can save more than 90% redundant transmission and increase the hybrid network throughput significantly

Newtonian nonlinear hydrodynamics and magnetohydrodynamics

We use covariant methods to analyse the nonlinear evolution of self-gravitating, non-relativistic media. The formalism is first applied to imperfect fluids, aiming at the kinematic effects of viscosity, before extended to inhomogeneous magnetised environments. The nonlinear electrodynamic formulae are derived and successively applied to electrically resistive and to highly conductive fluids. By nature, the covariant equations isolate the magnetic effects on the kinematics and the dynamics of the medium, combining mathematical transparency and physical clarity. Employing the Newtonian analogue of the relativistic 1+3 covariant treatment, also facilitates the direct comparison with the earlier relativistic studies and helps to identify the differences in an unambiguous way. The purpose of this work is to set the framework and take a first step towards the detailed analytical study of complex nonlinear systems, like non-relativistic astrophysical plasmas and collapsing protogalactic clouds.Comment: Typos corrected, references added and updated (MNRAS in press

Patrones de distribución de las comunidades de humedales patagónicos a una escala de paisaje.

Capítulo de libroEn este proyecto nos propusimos analizar los patrones de distribución de especies acuáticas en charcas de humedales patagónicos en relación con el encuadre hidrogeomorfológico, aspectos climáticos y el uso actual de la tierra y evaluar los cambios ambientales y las respuestas de las comunidades acuáticas (por ejemplo, invertebrados, macrófitas) en términos de diversidad, estructura y función frente a los cambios ambientales a diferentes escalas.Fil: Manzo, Luz M. Centro de Investigación Esquel de Montaña y Estepa Patagónica (CIEMEP) CONICET/UNPSJB, Chubut, Argentina. Email: [email protected]: Epele, Luis B.. Centro de Investigación Esquel de Montaña y Estepa Patagónica (CIEMEP) CONICET/UNPSJB, Chubut, Argentina. Email: [email protected]: Grech, Marta G.. Centro de Investigación Esquel de Montaña y Estepa Patagónica (CIEMEP) CONICET/UNPSJB, Chubut, Argentina. Email: [email protected]: Kandus, Patricia. Laboratorio de Ecología, Teledetección y Eco-Informática Instituto de Investigaciones e Ingeniería Ambiental, UNSAM, Argentina. Email: [email protected]: Miserendino, María L.. Centro de Investigación Esquel de Montaña y Estepa Patagónica (CIEMEP) CONICET/UNPSJB, Chubut, Argentina. Email: [email protected]

Gravitational wave amplification of seed magnetic fields

We discuss how gravitational waves could amplify seed magnetic fields to strengths capable of supporting the galactic dynamo. We consider the interaction of a weak magnetic field with gravity wave distortions in almost FRW cosmologies and find that the magnitude of the original field is amplified proportionally to the wave induced shear anisotropy and, crucially, proportionally to the square of the field's initial scale. The latter makes our mechanism particularly efficient when operating on superhorizon sized magnetic fields, like those produced during inflation. In that case, the achieved amplification can easily boost magnetic strengths, which may still lie relatively close to the galactic dynamo lower limits, well within the currently accepted range.Comment: Revised version, to appear in Phys. Lett.

Cosmological magnetic field survival

It is widely believed that primordial magnetic fields are dramatically diluted by the expansion of the universe. As a result, cosmological magnetic fields with residual strengths of astrophysical relevance are generally sought by going outside standard cosmology, or by extending conventional electromagnetic theory. Nevertheless, the survival of strong B-fields of primordial origin is possible in spatially open Friedmann universes without changing conventional electromagnetism. The reason is the hyperbolic geometry of these spacetimes, which slows down the adiabatic magnetic decay-rate and leads to their superadiabatic amplification on large scales. So far, the effect has been found to operate on Friedmannian backgrounds containing either radiation or a slow-rolling scalar field. We show here that the superadiabatic amplification of large-scale magnetic fields, generated by quantum fluctuations during inflation, is essentially independent of the type of matter that fills the universe and appears to be a generic feature of open Friedmann spacetimes. We estimate the late-time strength of any residual field in a marginally open universe and show that it can easily meet the requirements for the dynamo generation of the magnetic fields observed in galaxies today.Comment: Equations streamlined, references updated. MNRAS in pres

Supersymmetry Breaking through Transparent Extra Dimensions

We propose a new framework for mediating supersymmetry breaking through an extra dimension. It predicts positive scalar masses and solves the supersymmetric flavor problem. Supersymmetry breaks on a ``source'' brane that is spatially separated from a parallel brane on which the standard model matter fields and their superpartners live. The gauge and gaugino fields propagate in the bulk, the latter receiving a supersymmetry breaking mass from direct couplings to the source brane. Scalar masses are suppressed at the high scale but are generated via the renormalization group. We briefly discuss the spectrum and collider signals for a range of compactification scales.Comment: 20 page

Primordial magnetic fields from inflation?

The hot plasma above the electroweak scale contains (hyper) charged scalar particles which are coupled to Abelian gauge fields. Scalars may interact with gravity in a non-conformally invariant way and thus their fluctuations can be amplified during inflation. These fluctuations lead to creation of electric currents and produce inhomogeneous distribution of charge density, resulting in the generation of cosmological magnetic fields. We address the question whether these fields can be coherent at large scales so that they may seed the galactic magnetic fields. Depending upon the mass of the charged scalar and upon various cosmological (critical fraction of energy density in matter, Hubble constant) and particle physics parameters we found that the magnetic fields generated in this way are much larger than vacuum fluctuations. However, their amplitude on cosmological distances is found to be too small for seeding the galactic magnetic fields.Comment: 32 pages in RevTex styl

Superadiabatic-type magnetic amplification in conventional cosmology

We consider the evolution of cosmological magnetic fields in FRW models and outline a geometrical mechanism for their superadiabatic amplification on large scales. The mechanism operates within standard electromagnetic theory and applies to FRW universes with open spatial sections. We discuss the general relativistic nature of the effect and show how it modifies the adiabatic magnetic evolution. Assuming a universe that is only marginally open today, we estimate the main features of the superadiabatically amplified residual field.Comment: Minor changes. Published versio

Large-scale magnetic fields from inflation in dilaton electromagnetism

The generation of large-scale magnetic fields is studied in dilaton electromagnetism in inflationary cosmology, taking into account the dilaton's evolution throughout inflation and reheating until it is stabilized with possible entropy production. It is shown that large-scale magnetic fields with observationally interesting strength at the present time could be generated if the conformal invariance of the Maxwell theory is broken through the coupling between the dilaton and electromagnetic fields in such a way that the resultant quantum fluctuations in the magnetic field has a nearly scale-invariant spectrum. If this condition is met, the amplitude of the generated magnetic field could be sufficiently large even in the case huge amount of entropy is produced with the dilution factor $\sim 10^{24}$ as the dilaton decays.Comment: 28 pages, 5 figures, the version accepted for publication in Phys. Rev. D; some references are adde