Domain wall dynamics in an optical Kerr cavity

An anisotropic (dichroic) optical cavity containing a self-focusing Kerr medium is shown to display a bifurcation between static --Ising-- and moving --Bloch-- domain walls, the so-called nonequilibrium Ising-Bloch transition (NIB). Bloch walls can show regular or irregular temporal behaviour, in particular, bursting and spiking. These phenomena are interpreted in terms of the spatio-temporal dynamics of the extended patterns connected by the wall, which display complex dynamical behaviour as well. Domain wall interaction, including the formation of bound states is also addressed.Comment: 15 pages Tex file with 11 postscript figures. Resubmitted to Phys. Rev.

Implicaciones genéticas de nuevos datos de Sr y Nd de rocas intrusivas del Arco Laramide en el Norte de Sonora, México

The Laramide Intrusive Arc constitutes a wide intrusive belt broadly parallel to the actual Sonora coastline. It was formed by the subduction of the Farallon Plate beneath the North-American Plate during the Late Cretaceous-Early Tertiary period. New isotopic data on rocks of this arc show initial 87Sr/86Sr and eNd isotopic values of 0.7066 to 0.7070 and -5 to -6, respectively, for two samples from Bacanora area; as well as 0.7074 to 0.7081 and -3 to -5.5 respectively, for five samples from Cananea, Mariquita and La Caridad areas. Isotopic ages were determined by U/Pb in zircons (95 Ma) and Ar/Ar in potassic feldspar (56 to 71 Ma) from a quartz monzonite porphyry, and by Ar/Ar in potassic feldspar (56 Ma) from another plutonic granodiorite, both from Bacanora. Initial 87Sr/86Sr and eNd values for samples reported in this study suggest that the Laramidic magmas had a large influence from the Proterozoic basement in northeastern Sonora. Four different isotopic zones are proposed for Sonora, according with Sr-Nd data of laramidic rocks and the substratum intruded.El Arco Intrusivo Laramide constituye un amplio cinturón de rocas intrusivas orientado burdamente paralelo a la costa actual de Sonora. Este cinturón se originó por la subducción de la Placa Farallón bajo la Placa de Norteamérica durante el período Cretácico Tardío – Terciario Temprano. Nuevos datos isotópicos en rocas de este arco indican valores iniciales de 87Sr/86Sr y de eNd de 0.7066 a 0.7070 y -5 a -6, respectivamente, para dos muestras del área de Bacanora; así como de 0.7074 a 0.7081 y -3 a -5.5, respectivamente, para cinco muestras de las áreas de Cananea, Mariquita y La Caridad. Se determinaron también edades isotópicas por U/Pb en zircones (95 Ma) y Ar/Ar en feldespato potásico (56 a 71 Ma) para un pórfido de monzonita de cuarzo, y por Ar/Ar en feldespato potásico (56 Ma) para otra granodiorita plutónica, ambas de Bacanora. Los valores iniciales de 87Sr/86Sr y eNd para las muestras reportadas en este estudio, sugieren que los magmas laramídicos tuvieron gran influencia del basamento proterozoico en el noreste de Sonora. Cuatro diferentes zonas isotópicas son propuestas para Sonora, de acuerdo con los datos de Sr-Nd de las rocas laramídicas y el sustrato intrusionado

Spontaneous symmetry breaking as a resource for noncritically squeezed light

In the last years we have proposed the use of the mechanism of spontaneous symmetry breaking with the purpose of generating perfect quadrature squeezing. Here we review previous work dealing with spatial (translational and rotational) symmetries, both on optical parametric oscillators and four-wave mixing cavities, as well as present new results. We then extend the phenomenon to the polarization state of the signal field, hence introducing spontaneous polarization symmetry breaking. Finally we propose a Jaynes-Cummings model in which the phenomenon can be investigated at the single-photon-pair level in a non-dissipative case, with the purpose of understanding it from a most fundamental point of view.Comment: Review for the proceedings of SPIE Photonics Europe. 11 pages, 5 figures

Nonlinear optical Galton board

We generalize the concept of optical Galton board (OGB), first proposed by Bouwmeester et al. {[}Phys. Rev. A \textbf{61}, 013410 (2000)], by introducing the possibility of nonlinear self--phase modulation on the wavefunction during the walker evolution. If the original Galton board illustrates classical diffusion, the OGB, which can be understood as a grid of Landau--Zener crossings, illustrates the influence of interference on diffusion, and is closely connected with the quantum walk. Our nonlinear generalization of the OGB shows new phenomena, the most striking of which is the formation of non-dispersive pulses in the field distribution (soliton--like structures). These exhibit a variety of dynamical behaviors, including ballistic motion, dynamical localization, non--elastic collisions and chaotic behavior, in the sense that the dynamics is very sensitive to the nonlinearity strength.Comment: 8 pages, 8 figure

All-pass-filter-based active damping for VSCs with LCL filters connected to weak grids

LCL filters are commonly used to connect Voltage Sourced Converters (VSCs) to the grid. This type of filter is cheaper than a single inductor for the same current THD, but it generates resonance problems if no active or passive damping method is applied. Active damping methods are becoming popular in the literature because they improve efficiency, but they are sometimes difficult to implement and additional measurements are required. This paper proposes an active damping method for VSCs connected to weak grids that is based on making zero the open-loop phase at the resonance frequency. It will be shown that this strategy provides adequate damping of oscillations and that it can be achieved in two different ways: at the design stage (if the design constraints make it possible) or with an all-pass filter in series with the current controller. Two methods to design the all-pass filter are proposed. Also, the proposed active damping technique is compared with three alternatives already proposed in the literature. All the control algorithms are verified by simulation and in a 15 kW prototype of a three-phase VSC connected to a configurable weak grid via a LCL filter

Noncritical quadrature squeezing through spontaneous polarization symmetry breaking

We discuss the possibility of generating noncritical quadrature squeezing by spontaneous polarization symmetry breaking. We consider first type-II frequency-degenerate optical parametric oscillators, but discard them for a number of reasons. Then we propose a four-wave mixing cavity in which the polarization of the output mode is always linear but has an arbitrary orientation. We show that in such a cavity complete noise suppression in a quadrature of the output field occurs, irrespective of the parameter values

Squeezing spectra from s-ordered quasiprobability distributions. Application to dispersive optical bistability

It is well known that the squeezing spectrum of the field exiting a nonlinear cavity can be directly obtained from the fluctuation spectrum of normally ordered products of creation and annihilation operators of the cavity mode. In this article we show that the output field squeezing spectrum can be derived also by combining the fluctuation spectra of any pair of s-ordered products of creation and annihilation operators. The interesting result is that the spectrum obtained in this way from the linearized Langevin equations is exact, and this occurs in spite of the fact that no s-ordered quasiprobability distribution verifies a true Fokker-Planck equation, i.e., the Langevin equations used for deriving the squeezing spectrum are not exact. The (linearized) intracavity squeezing obtained from any s-ordered distribution is also exact. These results are exemplified in the problem of dispersive optical bistability.Comment: 15 pages, no figures, to be published in Journal of Modern Optic

Comparison of rainfall interception models in isolated individuals of Pinus pinea and Cistus ladanifer

[EN] This paper presents a comparison of several simulation models of interception process commonly used in numerous studies, such as the classic versions of Rutter and Gash, also the version of Valente adapted by sparse forests. The aim is to analyze the applicability of different models in isolated especimens of two species of Mediterranean climate, Pinus pinea and Cistus ladanifer. The data collection was carried out in the watershed of “El Cabril” (Córdoba), from October 2010 to June 2015. The differences obtained between measurements and the results of the different models are less than 6%. Original version of Rutter model and original version of Gash model present a greater adjustment for pine and for cistus respectively.[ES] En este trabajo se realiza una comparación de varios modelos de simulación del proceso de interceptación, comúnmente utilizados en numerosos estudios, como son las versiones clásicas de Rutter y de Gash, además de la versión adaptada por Valente a bosques dispersos. El objetivo es analizar la aplicabilidad de los diferentes modelos en ejemplares aislados de dos especies de clima mediterráneo, Pinus pinea y Cistus ladanifer. La toma de datos se ha realizado en la cuenca de “El Cabril” (Córdoba), desde octubre de 2010 a junio de 2015. Las diferencias obtenidas entre las medidas de campo y los resultados de los diferentes modelos son inferiores al 6%, siendo el modelo de Rutter en su versión original el que mejor se ajusta en pino y el modelo original de Gash el que mejor se ajusta en el caso de la jara.Este trabajo se desarrolló en el en el marco del proyecto de investigación “Balance hídrico superficial en la cuenca hidrológica de El Cabril” financiado por ENRESA (Empresa Nacional de Residuos Radiactivos) y la Universidad de Córdoba. Los autores desean expresar su agradecimiento al personal del Departamento de Ingeniería de Suelos de ENRESA por su continua y eficaz colaboración.Pérez-Arellano, R.; Moreno-Pérez, MF.; Roldán-Cañas, J. (2016). Comparación de modelos de interceptación de agua de lluvia en individuos aislados de Pinus pinea y Cistus ladanifer. Ingeniería del Agua. 20(3):153-168. doi:10.4995/ia.2016.4713.SWORD153168203Bellot, J. 1989. 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Contributions to Probability and Statistics: Essays in Honor of Harold Hotelling, Stanford University Press, 278-292.Llorens, P., Latron, J., Álvarez-Cobelas, M., Martínez-Vilalta, J., Moreno, G. 2011. Hydrology and biogeochemistry of Mediterranean forest. Forest Hydrology and Biogeochemistry. Ecological Studies, 216, 301-319. doi:10.1007/978-94-007-1363-5_14Llorens, P., Poch, R., Latron, J., Gallart, F. 1997. Rainfall interception by a Pinus sylvestris forest patch overgrown in a Mediterranean mountainous abandoned area. I. Monitoring design and results down to the event scale. Journal of Hydrology, 199(3-4), 331-345. doi:10.1016/S0022-1694(96)03334-3Loescher, H., Powers, J., Oberbauer, S. 2002. Spatial variation of throughfall volume in an old-growth tropical wet forest, Costa Rica. Journal of Tropical Ecology, 18(3), 397-407. doi:10.1017/S0266467402002274Massman, W. 1983. The derivation and validation of a new model for the interception of rainfall by forest. 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