Rotating vortex clusters in media with inhomogeneous defocusing   nonlinearity
  We show that media with inhomogeneous defocusing cubic nonlinearity growing toward the periphery can support a variety of stable vortex clusters nested in a common localized envelope. Nonrotating symmetric clusters are built of an even number of vortices with opposite topological charges, located at equal distances from the origin. Rotation makes the clusters strongly asymmetric, as the centrifugal force shifts some vortices to the periphery, while others approach the origin, depending on the topological charge. We obtain such asymmetric clusters as stationary states in the rotating coordinate frame, identify their existence domains, and show that the rotation may stabilize some of them. 
Yaroslav V. Kartashov, Boris A. Malomed, Victor A. Vysloukh, Milivoj   R. Belic, Lluis Torner
physics.optics cond-mat.quant-gas nlin.PS