Splitting in the Excitation Spectrum of A Bose-Einstein Condensate Undergoing Strong Rabi Oscillations

We report on a measurement of splitting in the excitation spectrum of a condensate driven by an optical travelling wave. Experimental results are compared to a numerical solution of the Gross Pitaevskii equation, and analyzed by a simple two level model and by the more complete band theory, treating the driving beams as an optical lattice. In this picture, the splitting is a manifestation of the energy gap between neighboring bands that opens on the boundary of the Brillouin zone.Comment: 5 pages, 5 figure

Scotland, Catalonia and the “right” to self-determination: a comment suggested by Kathryn Crameri’s “Do Catalans Have the Right to Decide?

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Decoherence and dephasing in strongly driven colliding Bose-Einstein condensates

We report on a series of measurements of decoherence and wavepacket dephasing between two colliding, strongly coupled, identical Bose-Einstein condensates. We measure, in the strong excitation regime, a suppression of the mean-field shift, compared to the shift which is observed for a weak excitation. This suppression is explained by applying the Gross-Pitaevskii energy functional. By selectively counting only the non-decohered fraction in a time of flight image we observe oscillations for which both inhomogeneous and Doppler broadening are suppressed, in quantitative agreement with a full Gross-Pitaevskii equation simulation. If no post selection is used, the decoherence rate due to collisions can be extracted, and is in agreement with the local density average calculated rate.Comment: 4 pages, 5 figure

Damping of bulk excitations over an elongated BEC - the role of radial modes

We report the measurement of Beliaev damping of bulk excitations in cigar shaped Bose Einstein condensates of atomic vapor. By using post selection, excitation line shapes of the total population are compared with those of the undamped excitations. We find that the damping depends on the initial excitation energy of the decaying quasi particle, as well as on the excitation momentum. We model the condensate as an infinite cylinder and calculate the damping rates of the different radial modes. The derived damping rates are in good agreement with the experimentally measured ones. The damping rates strongly depend on the destructive interference between pathways for damping, due to the quantum many-body nature of both excitation and damping products.Comment: 5 pages, 4 figure

Utility of Lymph Node Aspiration in the Diagnosis of Visceral Leishmaniasis in Sudan.

We evaluated lymph node aspiration (LNA) as a simple diagnostic procedure for visceral leishmaniasis (VL). Lymph node aspiration was compared with the direct agglutination test (DAT) using a diagnostic titer > or = 1:6,400 in 7,880 suspected VL patients in eastern Sudan. Compared with DAT, LNA had a sensitivity of 65.1% (95% confidence interval = 63.5-66.6%). Parasite density in LNA correlated strongly with DAT titers (P < 0.0001), and low parasite density accounted for 78.1% of positive LNA results with DAT titers < 1:6,400 (n = 782). Risk factors predictive of a positive LNA result were an age of 1-29 years, male sex, a hemoglobin level < 10.0 g/dL, a DAT titer > or = 1:800, and a location with a higher prevalence of VL. Lymph node and splenic aspirations were similarly accurate as tests of cure after treatment of 50 VL patients in southern Sudan. Pre-treatment LNA results were negative in 20 cases of severe post kala-azar dermal leishmaniasis

Echo spectroscopy of bulk Bogoliubov excitations in trapped Bose-Einstein condensates

We propose and demonstrate an echo method to reduce the inhomogeneous linewidth of Bogoliubov excitations, in a harmonically-trapped Bose-Einstein condensate. Our proposal includes the transfer of excitations with momentum +q to -q using a double two photon Bragg process, in which a substantial reduction of the inhomogeneous broadening is calculated. Furthermore, we predict an enhancement in the method's efficiency for low momentum due to many-body effects. The echo can also be implemented by using a four photon process, as is demonstrated experimentally.Comment: 4 pages, 5 figure

Collisional decay of a strongly driven Bose-Einstein condensate

We study the collisional decay of a strongly driven Bose-Einstein condensate oscillating between two momentum modes. The resulting products of the decay are found to strongly deviate from the usual s-wave halo. Using a stochastically seeded classical field method we simulate the collisional manifold. These results are also explained by a model of colliding Bloch states.Comment: 4 pages, 4 figure