  The effect of finite boundaries in the propagation of spatial nonlocal
solitons in media with cylindrical symmetry is analyzed. Using Ehrenfest's
theorem together with the Green's function of the nonlinear refractive index
equation, we derive an analytical expression for the force exerted on the
soliton by the boundaries, verifying its validity by full numerical
propagation. We show that the dynamics of the soliton are determined not only
by the degree of nonlocality, but also by the boundary conditions for the
refractive index. In particular, we report that a supercritical pitchfork
bifurcation appears when the boundary condition exceed a certain threshold
value.

Pattern Formation and Solitons;Optics