65,059 research outputs found
Transfer of BECs through discrete breathers in an optical lattice
We study the stability of a stationary discrete breather (DB) on a nonlinear
trimer in the framework of the discrete nonlinear Schr\"odinger equation
(DNLS). In previous theoretical investigations of the dynamics of Bose-Einstein
condensates in leaking optical lattices, collisions between a DB and a lattice
excitation, e.g. a moving breather (MB) or phonon, were studied. These
collisions lead to the transmission of a fraction of the incident (atomic) norm
of the MB through the DB, while the DB can be shifted in the direction of the
incident lattice excitation. Here we show that there exists a total energy
threshold of the trimer, above which the lattice excitation can trigger the
destabilization of the DB and that this is the mechanism leading to the
movement of the DB. Furthermore, we give an analytic estimate of upper bound to
the norm that is transmitted through the DB. Our analysis explains the results
of the earlier numerical studies and may help to clarify functional operations
with BECs in optical lattices such as blocking and filtering coherent (atomic)
beams.Comment: 8 pages, 5 figure
Single top production and decay at next-to-leading order
We present the results of a next-to-leading order analysis of single top
production including the decay of the top quark. Radiative effects are included
both in the production and decay stages, using a general subtraction method.
This calculation gives a good treatment of the jet activity associated with
single top production. We perform an analysis of the single top search at the
Tevatron, including a consideration of the main backgrounds, many of which are
also calculated at next-to-leading order.Comment: 35 pages + 15 figures, revtex
Production of a Z boson and two jets with one heavy-quark tag
We present a next-to-leading-order calculation of the production of a Z boson
with two jets, one or more of which contains a heavy quark (Q=c,b). We show
that the cross section with only one heavy-quark jet is larger than that with
two heavy-quark jets at both the Fermilab Tevatron and the CERN LHC. These
processes are the dominant irreducible backgrounds to a Higgs boson produced in
association with a Z boson, followed by h->bb. Our calculation makes use of a
heavy-quark distribution function, which resums collinear logarithms and makes
the next-to-leading-order calculation tractable.Comment: 11 pages, 5 figures. Erratum adde
Optimization of a Non-traditional Unsupervised Classification Approach for Land Cover Analysis
The conditions under which a hybrid of clustering and canonical analysis for image classification produce optimum results were analyzed. The approach involves generation of classes by clustering for input to canonical analysis. The importance of the number of clusters input and the effect of other parameters of the clustering algorithm (ISOCLS) were examined. The approach derives its final result by clustering the canonically transformed data. Therefore the importance of number of clusters requested in this final stage was also examined. The effect of these variables were studied in terms of the average separability (as measured by transformed divergence) of the final clusters, the transformation matrices resulting from different numbers of input classes, and the accuracy of the final classifications. The research was performed with LANDSAT MSS data over the Hazleton/Berwick Pennsylvania area. Final classifications were compared pixel by pixel with an existing geographic information system to provide an indication of their accuracy
Global Phase Space of Coherence and Entanglement in a double-well BEC
Ultracold atoms provide an ideal system for the realization of quantum
technologies, but also for the study of fundamental physical questions such as
the emergence of decoherence and classicality in quantum many-body systems.
Here, we study the global structure of the quantum dynamics of bosonic atoms in
a double-well trap and analyze the conditions for the generation of
many-particle entanglement and spin squeezing which have important applications
in quantum metrology. We show how the quantum dynamics is determined by the
phase space structure of the associated mean-field system and where true
quantum features arise beyond this `classical' approximation
Levi-Civita spacetimes in multidimensional theories
We obtain the most general static cylindrically symmetric vacuum solutions of
the Einstein field equations in dimensions. Under the assumption of
separation of variables, we construct a family of Levi-Civita-Kasner vacuum
solutions in . We discuss the dimensional reduction of the static
solutions. Depending on the reduction procedure, they can be interpreted either
as a scalar-vacuum generalization of Levi-Civita spacetimes, or as the
effective 4D vacuum spacetime outside of an idealized string in braneworld
theory.Comment: 7 pages. Accepted for publication in Mod. Phys. Lett. A (MPLA
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