Inferring long memory processes in the climate network via ordinal pattern analysis

We use ordinal patterns and symbolic analysis to construct global climate networks and uncover long and short term memory processes. The data analyzed is the monthly averaged surface air temperature (SAT field) and the results suggest that the time variability of the SAT field is determined by patterns of oscillatory behavior that repeat from time to time, with a periodicity related to intraseasonal oscillations and to El Ni\~{n}o on seasonal-to-interannual time scales.Comment: 10 pages, 13 figures Enlarged version, new sections and figures. Accepted in Chao

NLO predictions for the growth of F2F_2 at small xx and comparison with experimental data

We present parametrizations for the proton structure function $F_2$ in the next to leading order in perturbative QCD. The calculations show that the dominant term to $F_2(x,Q^2)$ should grow as x^{-\ls} for small $x$ values, with the exponent \ls being essentially independent of $Q^2$. Comparisons with the most recent H1 and ZEUS data confirm the value \ls \sim 0.35 obtained previously from fits to low energy data.Comment: 18 page

WMAP Constraints on a Quintessence Model

We use the results from the Wilkinson Microwave Anisotropy Probe (WMAP) for the locations of peaks and troughs of the Cosmic Microwave Background (CMB) power spectrum, together with constraints from large-scale structure, to study a quintessence model in which the pure exponential potential is modified by a polynomial factor. Our analysis, in the $(\Omega_m, h, n_s)$ cosmological parameters space shows that this quintessence model is favoured compared to $\Lambda$CDM for $n_s\approx 1$ and relatively high values of early quintessence; for $n_s<1$, quintessence and $\Lambda$CDM give similar results, except for high values of early quintessence, in which case $\Lambda$CDM is favoured.Comment: 3 pages. Talk presented by N. M. C. Santos at the Tenth Marcel Grossmann Meeting on General Relativity, Rio de Janeiro, July 200

A linear filter to reconstruct the ISW effect from CMB and LSS observations

The extraction of a signal from some observational data sets that contain different contaminant emissions, often at a greater level than the signal itself, is a common problem in Astrophysics and Cosmology. The signal can be recovered, for instance, using a simple Wiener filter. However, in certain cases, additional information may also be available, such as a second observation which correlates to a certain level with the sought signal. In order to improve the quality of the reconstruction, it would be useful to include as well this additional information. Under these circumstances, we have constructed a linear filter, the linear covariance-based filter, that extracts the signal from the data but takes also into account the correlation with the second observation. To illustrate the performance of the method, we present a simple application to reconstruct the so-called Integrated Sachs-Wolfe effect from simulated observations of the Cosmic Microwave Background and of catalogues of galaxies.Comment: 8 pages, 6 figures, accepted for publication in the IEEE Journal of Selected Topics in Signal Processin

Narrow band amplification of light carrying orbital angular momentum

We report on the amplification of an optical vortex beam carrying orbital angular momentum via induced narrow Raman gain in an ensemble of cold cesium atoms. A 20\% single-pass Raman gain of a weak vortex signal field is observed with a spectral width of order of 1 MHz, much smaller than the natural width, demonstrating that the amplification process preserves the phase structure of the vortex beam. The gain is observed in the degenerated two-level system associated with the hyperfine transition $6S_{1/2}(F=3)\leftrightarrow 6P_{3/2}(F^{\prime}=2)$ of cesium. Our experimental observations are explained with a simple theoretical model based on a three-level $\Lambda$ system interacting coherently with the weak Laguerre-Gauss field and a strong coupling field, including an incoherent pumping rate between the two degenerate ground-states.Comment: 9 pages, 4 figure

Deterministic creation of stationary entangled states by dissipation

We propose a practical physical system for creation of a stationary entanglement by dissipation without employing the environment engineering techniques. The system proposed is composed of two perfectly distinguishable atoms, through their significantly different transition frequencies, with only one atom addressed by an external laser field. We show that the arrangement would easily be realized in practice by trapping the atoms at the distance equal to the quarter-wavelength of a standing-wave laser field and locating one of the atoms at a node and the other at the successive antinode of the wave. The undesirable dipole-dipole interaction between the atoms, that could be large at this small distance, is adjusted to zero by a specific initial preparation of the atoms or by a specific polarization of the atomic dipole moments. Following this arrangement, we show that the dissipative relaxation can create a stationary entanglement on demand by tuning the Rabi frequency of the laser field to the difference between the atomic transition frequencies. The laser field dresses the atom and we identify that the entangled state occurs when the frequency of one of the Rabi sidebands of the driven atom tunes to frequency of the undriven atom. It is also found that this system behaves as a cascade open system where the fluorescence from the dressed atom drives the other atom with no feedback.Comment: Published versio

Polarization squeezing of light by single passage through an atomic vapor

We have studied relative-intensity fluctuations for a variable set of orthogonal elliptic polarization components of a linearly polarized laser beam traversing a resonant $^{87}$Rb vapor cell. Significant polarization squeezing at the threshold level (-3dB) required for the implementation of several continuous variables quantum protocols was observed. The extreme simplicity of the setup, based on standard polarization components, makes it particularly convenient for quantum information applications.Comment: Revised version. Minor changes. four pages, three figure

Translating sounds

P. 63-79El presente trabajo tiene como objetivo proporcionar información sobre cómo se reconocen y se traducen las palabras con programas de reconocimiento del habla. En la primera parte vamos a explicar brevemente la arquitectura de un programa de reconocimiento, basado en las plantillas, y los problemas que habitualmente se encuentran con este tipo de programas. En la segunda parte vamos a ofrecer una descripción detallada de las sesiones experimentales llevadas a cabo para comprobar el rendimiento del programar basado en plantillas con palabras aisladas y un pequeño vocabulario, con el problema añadido de múltiples altavoces con diferentes niveles de conocimiento de inglés. El análisis también incluirá comentarios sobre los patrones en el ordenamiento de los marcadores. Toda esta información puede ser relevante en la integración de estos sistemas en el proceso de enseñanza y aprendizaje de la pronunciación L