Collapse-driven spatiotemporal dynamics of filament formation
  The transition from spatial to spatiotemporal dynamics in Kerr-driven beam collapse is modelled as the instability of the Townes profile. Coupled axial and conical radiation, temporal splitting and X waves appear as the effect of Y-shaped unstable modes, whose growth is experimentally detected. 
Miguel A. Porras, Alberto Parola, Daniele Faccio, Arnaud Couairon,   Paolo Di Trapani