9,116 research outputs found
p-Wave Optical Feshbach Resonances in Yb-171
We study the use of an optical Feshbach resonance to modify the p-wave
interaction between ultracold polarized Yb-171 spin-1/2 fermions. A laser
exciting two colliding atoms to the 1S_0 + 3P_1 channel can be detuned near a
purely-long-range excited molecular bound state. Such an exotic molecule has an
inner turning point far from the chemical binding region and thus
three-body-recombination in the Feshbach resonance will be highly suppressed in
contrast to that typically seen in a ground state p-wave magnetic Feshbach
resonance. We calculate the excited molecular bound-state spectrum using a
multichannel integration of the Schr\"{o}dinger equation, including an external
perturbation by a magnetic field. From the multichannel wave functions, we
calculate the Feshbach resonance properties, including the modification of the
elastic p-wave scattering volume and inelastic spontaneous scattering rate. The
use of magnetic fields and selection rules for polarized light yields a highly
controllable system. We apply this control to propose a toy model for
three-color superfluidity in an optical lattice for spin-polarized Yb-171,
where the three colors correspond to the three spatial orbitals of the first
excited p-band. We calculate the conditions under which tunneling and on-site
interactions are comparable, at which point quantum critical behavior is
possible.Comment: 8 pages, 4 figure
TV News Story Segmentation Based on Semantic Coherence and Content Similarity
In this paper, we introduce and evaluate two novel approaches, one using video stream and the other using close-caption text stream, for segmenting TV news into stories. The segmentation of the video stream into stories is achieved by detecting anchor person shots and the text stream is segmented into stories using a Latent Dirichlet Allocation (LDA) based approach. The benefit of the proposed LDA based approach is that along with the story segmentation it also provides the topic distribution associated with each segment. We evaluated our techniques on the TRECVid 2003 benchmark database and found that though the individual systems give comparable results, a combination of the outputs of the two systems gives a significant improvement over the performance of the individual systems
Effect of mass asymmetry on the mass dependence of balance energy
We demonstrate the role of the mass asymmetry on the balance energy (Ebal) by
studying asymmetric reactions throughout the periodic table and over entire
colliding geometry. Our results, which are almost independent of the system
size and as well as of the colliding geometries indicate a sizeable effect of
the asymmetry of the reaction on the balance energy.Comment: Journal of Physics - Conference Series - Online end of March (2011
Bulk Viscosity of Magnetized Neutron Star Matter
We study the effect of magnetic field on the bulk viscosity of nuclear matter
in neutron stars. We employ the framework of relativistic mean field theory to
observe the dense nuclear matter in neutron stars. The effects are first
studied for the case when the magnetic field does not exceed the critical value
to confine the electrons to the lowest Landau levels. We then consider the case
of intense magnetic field to evaluate viscosity for the URCA processes and show
that the inequality is no longer required to
be satisfied for the URCA processes to proceed.Comment: Latex 2e file with four postscripts figure
Matching and Network Effects
This paper examines the existence and magnitude of network effects in the matching of workteams. We study the formation of co-author relations among economists over a thirty year period. Our principal finding is that a collaboration emerges faster among two authors if they are closer in the social network of economists. This proximity effect on collaboration is strong and robust but only affects initial collaboration. It has no positive influence on subsequent co-authorship. We also provide some evidence that matching depends on experience, junior authors being more likely to collaborate with senior authors.
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