  Vortex solitons (dark solitons) are described in self-defocusing Kerr media
whose phase line singularity is not parallel to the propagation direction, but
is perpendicular or tilted almost arbitrary angles, depending on the medium
linear dispersion. These solitons broaden the so-called spatiotemporal optical
vortices recently observed in experiments to the nonlinear realm, opening new
perspectives in practical applications of optical vortices.
