271 research outputs found
First Observational Tests of Eternal Inflation: Analysis Methods and WMAP 7-Year Results
In the picture of eternal inflation, our observable universe resides inside a
single bubble nucleated from an inflating false vacuum. Many of the theories
giving rise to eternal inflation predict that we have causal access to
collisions with other bubble universes, providing an opportunity to confront
these theories with observation. We present the results from the first
observational search for the effects of bubble collisions, using cosmic
microwave background data from the WMAP satellite. Our search targets a generic
set of properties associated with a bubble collision spacetime, which we
describe in detail. We use a modular algorithm that is designed to avoid a
posteriori selection effects, automatically picking out the most promising
signals, performing a search for causal boundaries, and conducting a full
Bayesian parameter estimation and model selection analysis. We outline each
component of this algorithm, describing its response to simulated CMB skies
with and without bubble collisions. Comparing the results for simulated bubble
collisions to the results from an analysis of the WMAP 7-year data, we rule out
bubble collisions over a range of parameter space. Our model selection results
based on WMAP 7-year data do not warrant augmenting LCDM with bubble
collisions. Data from the Planck satellite can be used to more definitively
test the bubble collision hypothesis.Comment: Companion to arXiv:1012.1995. 41 pages, 23 figures. v2: replaced with
version accepted by PRD. Significant extensions to the Bayesian pipeline to
do the full-sky non-Gaussian source detection problem (previously restricted
to patches). Note that this has changed the normalization of evidence values
reported previously, as full-sky priors are now employed, but the conclusions
remain unchange
Super-poissonian photon statistics and correlations between pump and probe fields in Electromagnetically Induced Transparency
We have measured the photon statistics of pump and probe beams after
interaction with Rb atoms in a situation of Electromagnetically Induced
Transparency. Both fields present super-poissonian statistics and their
intensities become correlated, in good qualitative agreement with theoretical
predictions in which both fields are treated quantum-mechanically. The
intensity correlations measured are a first step towards the observation of
entanglement between the fields.Comment: 4 pages, two-column, 4 figures, first submitted to PRL on Aug. 6,
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Laser-noise-induced correlations and anti-correlations in Electromagnetically Induced Transparency
High degrees of intensity correlation between two independent lasers were
observed after propagation through a rubidium vapor cell in which they generate
Electromagnetically Induced Transparency (EIT). As the optical field
intensities are increased, the correlation changes sign (becoming
anti-correlation). The experiment was performed in a room temperature rubidium
cell, using two diode lasers tuned to the Rb line (nm). The cross-correlation spectral function for the pump and probe fields
is numerically obtained by modeling the temporal dynamics of both field phases
as diffusing processes. We explored the dependence of the atomic response on
the atom-field Rabi frequencies, optical detuning and Doppler width. The
results show that resonant phase-noise to amplitude-noise conversion is at the
origin of the observed signal and the change in sign for the correlation
coefficient can be explained as a consequence of the competition between EIT
and Raman resonance processes.Comment: Accepted for publication in EPJ
Transcriptional Regulation of zma-MIR528a by Action of Nitrate and Auxin in Maize
In recent years, miR528, a monocot-specific miRNA, has been assigned multifaceted roles during development and stress response in several plant species. However, the transcription regulation and the molecular mechanisms controlling MIR528 expression in maize are still poorly explored. Here we analyzed the zma-MIR528a promoter region and found conserved transcription factor binding sites related to diverse signaling pathways, including the nitrate (TGA1/4) and auxin (AuxRE) response networks. Accumulation of both pre-miR528a and mature miR528 was up-regulated by exogenous nitrate and auxin treatments during imbibition, germination, and maize seedling establishment. Functional promoter analyses demonstrated that TGA1/4 and AuxRE sites are required for transcriptional induction by both stimuli. Overall, our findings of the nitrogen- and auxin-induced zma-MIR528a expression through cis-regulatory elements in its promoter contribute to the knowledge of miR528 regulome
Scalar fields in an anisotropic closed universe
We study in this article a class of homogeneous, but anisotropic cosmological
models in which shear viscosity is included. Within the matter content we
consider a component (the quintessence component) determined by the barotropic
equations of state, , with . We establish conditions
under which a closed axisymmetrical cosmological model may look flat al low
redshift.Comment: 6 pages, Latex, 2 figures, accepted in Phys. Rev.
Influencia de variables meteorológicas sobre el rendimiento de la caña de azúcar
Se seleccionaron 14 ingenios azucareros pertenecientes a las provincias Artemisa, Mayabeque y Matanzas, con sus respectivas estaciones meteorológicas asociadas. Los datos anuales de rendimiento agrícola e industrial de la caña de azúcar y los registros diarios de precipitaciones y temperaturas en el período comprendido entre 1980 y 2011 (30 años), sirvieron de base para el estudio. El análisis de los datos arrojó que en todo el período, la temperatura máxima (Tmáx) no experimentó cambios, la temperatura media (Tm) aumentó en 0,93ºC, mientras que la temperatura mínima (Tmín) lo hizo en 0,62ºC y la amplitud térmica (AT) se redujo en 0,72ºC. De todas las regiones estudiadas, la estación meteorológica de Bahía Honda fue la que mostró los menores valores de AT. Las precipitaciones incrementaron en 33,78%, mientras que RA disminuyó en 52,83% con relación a su valor inicial. Se encontró una dependencia inversa entre la AT y la Tmín, mientras que hubo una fuerte dependencia entre RI y Prec (97%) en las tres provincias. Estas últimas, 10 días antes de la cosecha, tuvieron un ligero efecto negativo sobre RI, en tanto que, éste no fue prácticamente afectado. Se concluyó que la provincia Matanzas fue la que presentó las mejores condiciones climáticas para el cultivo de la caña de azúcar y dentro de ella, la zona más propicia para su desarrollo fue el municipio Jovellanos
Dynamics of a thin shell in the Reissner-Nordstrom metric
We describe the dynamics of a thin spherically symmetric gravitating shell in
the Reissner-Nordstrom metric of the electrically charged black hole. The
energy-momentum tensor of electrically neutral shell is modelled by the perfect
fluid with a polytropic equation of state. The motion of a shell is described
fully analytically in the particular case of the dust equation of state. We
construct the Carter-Penrose diagrams for the global geometry of the eternal
black hole, which illustrate all possible types of solutions for moving shell.
It is shown that for some specific range of initial parameters there are
possible the stable oscillating motion of the shell transferring it
consecutively in infinite series of internal universes. We demonstrate also
that this oscillating type of motion is possible for an arbitrary polytropic
equation of state on the shell.Comment: 17 pages, 7 figure
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