Variational approach to bistable solitary waves of the first kind in d dimensions.

The variational approach has been applied to a study of bistable solitary waves of the first kind in d dimensions for some illustrative models. In particular, energy formulas and bistability criterion have been derived and the variational results compared with those obtained numerically. In one dimension the agreement is found to be excellent. As d is increased, the agreement decreases despite the fact that flexibility was built into the trial wave function. The implications for successfully treating the threedimensional light-bullet problem are discussed