Tensorial perturbations in the bulk of inflating brane worlds

In this paper we consider the stability of some inflating brane-world models in quantum cosmology. It is shown that whereas the singular model based on the construction of inflating branes from Euclidean five-dimensional anti-de Sitter space is unstable to tensorial cosmological perturbations in the bulk, the nonsingular model which uses a five-dimensional asymptotically anti-de Sitter wormhole to construct the inflating branes is stable to these perturbations.Comment: 4 pages, RevTex, to appear in Phys. Rev.

A dark energy multiverse

We present cosmic solutions corresponding to universes filled with dark and phantom energy, all having a negative cosmological constant. All such solutions contain infinite singularities, successively and equally distributed along time, which can be either big bang/crunchs or big rips singularities. Classicaly these solutions can be regarded as associated with multiverse scenarios, being those corresponding to phantom energy that may describe the current accelerating universe

Modelling of chemical control of "Conyza" and the risk of glyphosate resistance

Se ha desarrollado un modelo de genética de poblaciones para estudiar el efecto de diferentes estrategias de manejo químicas en el control de poblaciones de Conyza y el desarrollo de resistencia a glifosato en poblaciones inicialmente susceptibles. Las estrategias de manejo se basaron en la aplicación de dos herbicidas en diferentes fechas, aislados o en mezcla, donde uno de ellos era glifosato. Las simulaciones mostraron que la aplicación de glifosato con herbicidas postemergentes controlaron más eficazmente las poblaciones de “Conyza” que las aplicaciones de glifosato con herbicidas preemergentes. Las aplicaciones tardías (principalmente en marzo) del herbicida postemergente consiguieron los mejores controles de las poblaciones y un riesgo bajo de desarrollar resistencia en poblaciones de Conyza inicialmente susceptibles.We developed a model of population genetics to study the effect of different chemical management strategies on the control of “Conyza” populations and the resistance evolution to glyphosate in initially susceptible populations. The management strategies were based on herbicides; glyphosate and another post- or pre-emergent herbicide applied alone or in mixtures at different timing. The simulations showed that glyphosate and post-emergent herbicides controlled better “Conyza” populations than glyphosate and pre-emergent herbicides. Later post-emergent herbicide applications (in March principally) reached the best control of “Conyza” populations and a low resistance risk in initially susceptible populations

A graceful multiversal link of particle physics to cosmology

In this paper we work out a multiverse scenario whose physical characteristics enable us to advance the following the conjecture that whereas the physics of particles and fields is confined to live in the realm of the whole multiverse formed by finite-time single universes, that for our observable universe must be confined just in one of the infinite number of universes of the multiverse when such a universe is consistently referred to an infinite cosmic time. If this conjecture is adopted then some current fundamental problems that appear when one tries to make compatible particle physics and cosmology- such as that for the cosmological constant, the arrow of time and the existence of a finite proper size of the event horizon- can be solved.Comment: 10 pages, LaTe

Self-similar transmission properties of aperiodic Cantor potentials in gapped graphene

We investigate the transmission properties of quasiperiodic or aperiodic structures based on graphene arranged according to the Cantor sequence. In particular, we have found self-similar behaviour in the transmission spectra, and most importantly, we have calculated the scalability of the spectra. To do this, we implement and propose scaling rules for each one of the fundamental parameters: generation number, height of the barriers and length of the system. With this in mind we have been able to reproduce the reference transmission spectrum, applying the appropriate scaling rule, by means of the scaled transmission spectrum. These scaling rules are valid for both normal and oblique incidence, and as far as we can see the basic ingredients to obtain self-similar characteristics are: relativistic Dirac electrons, a self-similar structure and the non-conservation of the pseudo-spin. This constitutes a reduction of the number of conditions needed to observe self-similarity in graphene-based structures, see D\'iaz-Guerrero et al. [D. S. D\'iaz-Guerrero, L. M. Gaggero-Sager, I. Rodr\'iguez-Vargas, and G. G. Naumis, arXiv:1503.03412v1, 2015]

Short communication. Modelling of the population dynamics of Phalaris brachystachys Link under various herbicide control scenarios in a Mediterranean climate

The weed Phalaris brachystachys Link (short-spiked canarygrass) severely affects cereal production in regions with a Mediterranean climate. A mathematical model for simulating the population dynamics of this weed was constructed using previously reported brachystachys populations

Up to fifth-order Raman scattering of InP under nonresonant conditions

We present Raman spectra of InP measured under nonresonant conditions revealing multiphonon processes up to fifth order. Using an incident photon energy in the absorption region of the compound but far from any of its interband transitions, nonresonant multiphonon processes of order higher than two, which have not been reported so far in a zinc-blende-type semiconductor, have been observed in indium phosphide. In this way it has been possible to detect contributions not only from the longitudinal optical phonons but also from the transverse optical phonons in the higher-order peaks. We find a very good agreement between multiples of the TO- and LO-phonon frequencies at the zone center and the higher-order phonons measured in the experiments. The trend of strong intensity reductions observed when passing from first to second as well as from second to third order is not maintained when going from third to fourth, and from fourth to fifth order