Merging of vortices and antivortices in polariton superfluids

Quantised vortices are remarkable manifestations on a macroscopic scale of the coherent nature of quantum fluids, and the study of their properties is of fundamental importance for the understanding of this peculiar state of matter. Cavity-polaritons, due to their double light-matter nature, offer a unique controllable environment to investigate these properties. In this work we theoretically investigate the possibility to deterministically achieve the annihilation of a vortex with an antivortex through the increase of the polariton density in the region surrounding the vortices. Moreover we demonstrate that by means of this mechanism an array of vortex-antivortex pairs can be completely washed out

Interaction-shaped vortex-antivortex lattices in polariton fluids

Topological defects such as quantized vortices are one of the most striking manifestations of the superfluid nature of Bose-Einstein condensates and typical examples of quantum mechanical phenomena on a macroscopic scale. Here we demonstrate the formation of a lattice of vortex-antivortex pairs and study, for the first time, its properties in the non-linear regime at high polarion-density where polariton-polariton interactions dominate the behaviour of the system. In this work first we demonstrate that the array of vortex-antivortex pairs can be generated in a controllable way in terms of size of the array and in terms of size and shape of it fundamental unit cell. Then we demonstrate that polariton-polariton repulsion can strongly deform the lattice unit cell and determine the pattern distribution of the vortex-antivortex pairs, reaching a completely new behaviour with respect to geome

All -optical control of the quantum flow of a polariton condensate

Although photons in vacuum are massless particles that do not appreciably interact with each other, significant interactions appear in suitable nonlinear media, leading to hydrodynamic behaviours typical of quantum fluids(1-6). Here, we show the generation and manipulation of vortex-antivortex pairs in a coherent gas of strongly dressed photons (polaritons) flowing against an artificial potential barrier created and controlled by a light beam in a semiconductor microcavity. The optical control of the polariton flow allows us to reveal new quantum hydrodynamical phenomenologies such as the formation of vortex pairs upstream from the optical barrier, a case of ultra-short time excitation of the quantum flow, and the generation of vortices with counterflow trajectories. Additionally, we demonstrate how to permanently trap and store quantum vortices hydrodynamically generated in the wake of a defect. These observations are supported by time-dependent simulations based on the non-equilibrium Gross-Pitaevskii equation(7)

Mitral valve prolapse associated with celiac artery stenosis: a new ultrasonographic syndrome?

BACKGROUND: Celiac artery stenosis (CAS) may be caused by atherosclerotic degeneration or compression exerted by the arched ligament of the diaphragm. Mitral valve prolapse (MVP) is the most common valvular disorder. There are no reports on an association between CAS and MVP. METHODS: 1560 (41%) out of 3780 consecutive patients undergoing echocardiographic assessment of MVP, had Doppler sonography of the celiac tract to detect CAS. RESULTS: CAS was found in 57 (3.7%) subjects (23 males and 34 females) none of whom complained of symptoms related to visceral ischemia. MVP was observed in 47 (82.4%) subjects with and 118 (7.9%) without CAS (p < 0.001). The agreement between MVP and CAS was 39% (95% CI 32–49%). PSV (Peak Systolic Velocity) was the only predictor of CAS in MPV patients (OR 0.24, 95% CI 0.08–0.69) as selected in a multivariate logistic model. CONCLUSION: CAS and MVP seem to be significantly associated in patients undergoing consecutive ultrasonographic screening

Simulation-based investigations on the drape behavior of 3D woven fabrics made of commingled yarns

International audienceComposites based on 3D woven fabrics offer excellent mechanical properties due to the nearly non-crimp reinforcement fibers. Additionally, a reduced number of process steps results from the 3D nature of the reinforcement. Their in-plane and out-of-plane behaviors are purposefully adjustable to the expected loading conditions. A previously introduced modelling approach is extended to the simulation of 3D woven fabrics. The tensile, shear and bending behaviors of the fabric are considered in a material formulation for large deformations using shell elements. The model is successfully validated and parameter studies show the significant influence of shear and bending parameters on forming results. Furthermore, it is shown that also the forming process parameters have a significant influence on the draping results. It is concluded that the shearing and wrinkling can be reduced to a minimum with adapted material and process parameters