Nonlocal stabilization of nonlinear beams in a self-focusing atomic   vapor
  We show that ballistic transport of optically excited atoms in an atomic vapor provides a nonlocal nonlinearity which stabilizes the propagation of vortex beams and higher order modes in the presence of a self-focusing nonlinearity. Numerical experiments demonstrate stable propagation of lowest and higher order vortices over a hundred diffraction lengths, before dissipation leads to decay of these structures. 
S. Skupin, M. Saffman, and W. Krolikowski