25,467 research outputs found
Suspensions Thermal Noise in the LIGO Gravitational Wave Detector
We present a calculation of the maximum sensitivity achievable by the LIGO
Gravitational wave detector in construction, due to limiting thermal noise of
its suspensions. We present a method to calculate thermal noise that allows the
prediction of the suspension thermal noise in all its 6 degrees of freedom,
from the energy dissipation due to the elasticity of the suspension wires. We
show how this approach encompasses and explains previous ways to approximate
the thermal noise limit in gravitational waver detectors. We show how this
approach can be extended to more complicated suspensions to be used in future
LIGO detectors.Comment: 28 pages, 13 figure
Exciton Gas Compression and Metallic Condensation in a Single Semiconductor Quantum Wire
We study the metal-insulator transition in individual self-assembled quantum
wires and report optical evidences of metallic liquid condensation at low
temperatures. Firstly, we observe that the temperature and power dependence of
the single nanowire photoluminescence follow the evolution expected for an
electron-hole liquid in one dimension. Secondly, we find novel spectral
features that suggest that in this situation the expanding liquid condensate
compresses the exciton gas in real space. Finally, we estimate the critical
density and critical temperature of the phase transition diagram at
cm and K, respectively.Comment: 4 pages, 5 figure
Tunable entanglement distillation of spatially correlated down-converted photons
We report on a new technique for entanglement distillation of the bipartite
continuous variable state of spatially correlated photons generated in the
spontaneous parametric down-conversion process (SPDC), where tunable
non-Gaussian operations are implemented and the post-processed entanglement is
certified in real-time using a single-photon sensitive electron multiplying CCD
(EMCCD) camera. The local operations are performed using non-Gaussian filters
modulated into a programmable spatial light modulator and, by using the EMCCD
camera for actively recording the probability distributions of the
twin-photons, one has fine control of the Schmidt number of the distilled
state. We show that even simple non-Gaussian filters can be finely tuned to a
~67% net gain of the initial entanglement generated in the SPDC process.Comment: 12 pages, 6 figure
Combinatorics of lattice paths with and without spikes
We derive a series of results on random walks on a d-dimensional hypercubic
lattice (lattice paths). We introduce the notions of terse and simple paths
corresponding to the path having no backtracking parts (spikes). These paths
label equivalence classes which allow a rearrangement of the sum over paths.
The basic combinatorial quantities of this construction are given. These
formulas are useful when performing strong coupling (hopping parameter)
expansions of lattice models. Some applications are described.Comment: Latex. 25 page
Statics, Dynamics and Manipulations of Bright Matter-Wave Solitons in Optical Lattices
Motivated by recent experimental achievement in the work with Bose-Einstein
condensates (BECs), we consider bright matter-wave solitons, in the presence of
a parabolic magnetic trap and a spatially periodic optical lattice (OL), in the
attractive BEC. We examine pinned states of the soliton and their stability by
means of perturbation theory. The analytical predictions are found to be in
good agreement with numerical simulations. We then explore possibilities to use
a time-modulated OL as a means of stopping and trapping a moving soliton, and
of transferring an initially stationary soliton to a prescribed position by a
moving OL. We also study the emission of radiation from the soliton moving
across the combined magnetic trap and OL. We find that the soliton moves freely
(without radiation) across a weak lattice, but suffers strong loss for stronger
OLs.Comment: 7 pages, 5 figs, Phys Rev A in Press (2005
Metastable anisotropy orientation of nematic quantum Hall fluids
We analyze the experimental observation of metastable anisotropy resistance
orientation at half filled quantum Hall fluids by means of a model of a quantum
nematic liquid in an explicit symmetry breaking potential. We interpret the
observed ``rotation'' of the anisotropy axis as a process of nucleation of
nematic domains and compute the nucleation rate within this model. By comparing
with experiment, we are able to predict the critical radius of nematic bubbles,
. Each domain contains about electrons.Comment: 10 pages, 8 figures, final version as will appear in PR
Anti-de Sitter wormhole kink
The metric describing a given finite sector of a four-dimensional
asymptotically anti-de Sitter wormhole can be transformed into the metric of
the time constant sections of a Tangherlini black hole in a five-dimensional
anti-de Sitter spacetime when one allows light cones to tip over on the
hypersurfaces according to the conservation laws of an one-kink. The resulting
kinked metric can be maximally extended, giving then rise to an instantonic
structure on the euclidean continuation of both the Tangherlini time and the
radial coordinate. In the semiclassical regime, this kink is related to the
existence of closed timelike curves.Comment: 10 pages, to appear in IJMP
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