Globally-Linked Vortex Clusters in Trapped Wave Fields
  We put forward the existence of a rich variety of fully stationary vortex structures, termed H-clusters, made of an increasing number of vortices nested in paraxial wave fields confined by trapping potentials. However, we show that the constituent vortices are globally linked, rather than products of independent vortices. Also, they always feature a monopolar global wave front and exist in nonlinear systems, such as Bose-Einstein condensates. Clusters with multipolar global wave fronts are non-stationary or at best flipping. 
Lucian-Cornel Crasovan, Gabriel Molina-Terriza, Juan P. Torres, Lluis   Torner, Victor M. Perez-Garcia, Dumitru Mihalache