Modulation of a quantized vortex street with a vibrating obstacle

Dynamics of a superfluid flow past an obstacle are investigated by solving the Gross-Pitaevskii equation numerically. For an appropriate velocity and size of the obstacle, quantized vortices are periodically generated in the wake, which form a Benard-von Karman vortex street. It is found that vibration of an obstacle modulates the vortex street breaking a symmetry.Comment: 6 pages, 5 figures, Proceedings of IUTAM Symposium 2012: "Understanding Common Aspects of Extreme Events in Fluids"; Sec 3.2 extende

Penetration of a vortex dipole across an interface of Bose-Einstein condensates

The dynamics of a vortex dipole in a quasi-two dimensional two-component Bose-Einstein condensate are investigated. A vortex dipole is shown to penetrate the interface between the two components when the incident velocity is sufficiently large. A vortex dipole can also disappear or disintegrate at the interface depending on its velocity and the interaction parameters.Comment: 7 pages, 9 figure

Order-disorder oscillations in exciton-polariton superfluids

The dynamics of an exciton-polariton superfluid resonantly pumped in a semiconductor microcavity are investigated by mean-field theory. Modulational instability develops into crystalline order and then ordered and disordered states alternately form. A supersolid-like state is also found, in which superflow coexists with crystalline order at rest.Comment: 5 pages, 3 figures, 6 movie

Controlled generation and manipulation of vortex dipoles in a Bose-Einstein condensate

We propose methods to generate and manipulate vortex dipoles in a Bose-Einstein condensate using Gaussian beams of red or blue-detuned laser. Velocity-controlled vortex dipoles are shown to be created and launched by a red-detuned beam and by two blue-detuned beams. Critical velocities for the vortex nucleation are investigated. The launched vortex dipoles can be trapped, curved, accelerated, and decelerated using Gaussian beams. Collisions between vortex dipoles are demonstrated.Comment: 9 pages, 10 figure

Occurrence of the eelgrass pathogen, Labyrinthula zosterae, in Japan

The marine slime mold Labyrinthula zosterae, the causative agent of wasting disease of eelgrass Zostera marina, has been isolated from both 2. marina and 2. caulescens on the south coast of Japan. In addition, wasting-disease symptoms were produced in disease tests on leaves of Z. japonica and 2. marina using axenic cultures of L. zosterae isolated from Z. caulescens and Z. marina. Thus, the known host species of L. zosterae are expanded to include 3 species of Zostera. Although symptomatic necrotic lesions were observed in field-collected seagrass leaves, widespread die-off from wasting disease was not evident on the south coast of Japan

Symmetry breaking Rayleigh-Taylor instability in a two-component Bose-Einstein condensate

The interfacial instability and subsequent dynamics in a phase-separated two-component Bose-Einstein condensate with rotation symmetry are studied. When the interatomic interaction or the trap frequency is changed, the Rayleigh-Taylor instability breaks the rotation symmetry of the interface, which is subsequently deformed into nonlinear patterns including mushroom shapes.Comment: 5 pages, 5 figure

B\'enard-von K\'arm\'an vortex street in an exciton-polariton superfluid

The dynamics of an exciton--polariton superfluid resonantly injected into a semiconductor microcavity are investigated numerically. The results reveal that a B\'enard--von K\'arm\'an vortex street is generated in the wake behind an obstacle potential, in addition to the generation of quantized vortex dipoles and dark solitons. The vortex street is shown to be robust against a disorder potential in a sample and it can be observed even in time-integrated measurements.Comment: 4 pages, 3 figure