Stabilization of a light bullet in a layered Kerr medium with   sign-changing nonlinearity
  Using the numerical solution of the nonlinear Schr\"odinger equation and a variational method it is shown that (3+1)-dimensional spatiotemporal optical solitons, known as light bullets, can be stabilized in a layered Kerr medium with sign-changing nonlinearity along the propagation direction. 
Sadhan K. Adhikari