277 research outputs found
The Atomic Lighthouse Effect
We investigate the deflection of light by a cold atomic cloud when the
light-matter interaction is locally tuned via the Zeeman effect using magnetic
field gradients. This "lighthouse" effect is strongest in the single-scattering
regime, where deviation of the incident field is largest. For optically dense
samples, the deviation is reduced by collective effects, as the increase in
linewidth leads to a decrease of the magnetic field efficiency
Spatial and temporal localization of light in two dimensions
Quasi-resonant scattering of light in two dimensions can be described either
as a scalar or as a vectorial electromagnetic wave. Performing a scaling
analysis we observe in both cases long lived modes, yet only the scalar case
exhibits Anderson localized modes together with extremely long mode lifetimes.
We show that the localization length of these modes is influenced only by their
position, and not their lifetime. Investigating the reasons for the absence of
localization, it appears that both the coupling of several polarizations and
the presence of near-field terms are able to prevent long lifetimes and
Anderson localization.Comment: 5 pages, 4 figures and Supplementary Informatio
Variational Methods in AdS/CFT
We prove that the AdS/CFT calculation of 1-point functions can be drastically
simplified by using variational arguments. We give a simple universal proof,
valid for any theory that can be derived from a Lagrangian, that the large
radius divergencies in 1-point functions can always be renormalized away (at
least in the semiclassical approximation). The renormalized 1-point functions
then follow by a simple variational problem involving only finite quantities.
Several examples, a massive scalar, gravity, and renormalization flows, are
discussed. Our results are general and can thus be used for dualities beyond
AdS/CFT.Comment: 14 pages, no figures, LaTeX, minor change in footnot
A tensor instability in the Eddington inspired Born-Infeld Theory of Gravity
In this paper we consider an extension to Eddington's proposal for the
gravitational action. We study tensor perturbations of a homogeneous and
isotropic space-time in the Eddington regime, where modifications to Einstein
gravity are strong. We find that the tensor mode is linearly unstable deep in
the Eddington regime and discuss its cosmological implications.Comment: 5 pages, approved by Phys. Rev. D, additional references and minor
modification
Eddington-Born-Infeld action for dark energy and dark matter
We argue that Einstein gravity coupled to a Born-Infeld theory provides an
attractive candidate to represent dark matter and dark energy. For cosmological
models, the Born-Infeld field has an equation of state which interpolates
between matter, w=0 (small times), and a cosmological constant w=-1 (large
times). On galactic scales, the Born-Infeld field predicts asymptotically flat
rotation curves.Comment: A sign mistake in section on galactic scales is pointed out. This
sign invalidates the content of that section. See comment on manuscrip
La investigación forestal y su impacto en la producción
Haciendo un recorrido por la empresa Fiplasto y sus investigaciones de materiales para mejorar sus productos, se desarrollo el tema de investigación forestal, especies, producción y economía.Trabajo galardonado con el Premio Academia Nacional de Agronomía y Veterinaria, versión 2003.Academia Nacional de Agronomía y Veterinari
La investigación forestal y su impacto en la producción
Haciendo un recorrido por la empresa Fiplasto y sus investigaciones de materiales para mejorar sus productos, se desarrollo el tema de investigación forestal, especies, producción y economía.Trabajo galardonado con el Premio Academia Nacional de Agronomía y Veterinaria, versión 2003.Academia Nacional de Agronomía y Veterinari
Sensitivity of electromagnetically induced transparency to light-mediated interactions
Here we present a microscopic model that describes the Electromagnetically
Induced Transparency (EIT) phenomenon in the multiple scattering regime. We
consider an ensemble of cold three-level atoms, in a configuration,
scattering a probe and a control field to the vacuum modes of the
electromagnetic field. By first considering a scalar description of the
scattering, we show that the light-mediated long-range interactions that emerge
between the dipoles narrow the EIT transparency window for increasing densities
and sample sizes. For a vectorial description, we demonstrate that near-field
interacting terms can critically affect the atomic population transfer in the
Stimulated Raman Adiabatic Passage (STIRAP). This result points out that
standard STIRAP-based quantum memories in cold atomic ensembles would not reach
high enough efficiencies for quantum information processing applications even
in dilute regimes.Comment: 9 pages, 5 figure
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