  Skyrmions in an antiferromagnet can travel as solitary waves in stark
contrast to the situation in ferromagnets. Traveling skyrmion solutions have
been found numerically in chiral antiferromagnets. We consider head-on
collision events between two skyrmions. We find that the result of the
collision depends on the initial velocity of the skyrmions. For small
velocities, the skyrmions are shrinking as they are approaching, they bounce
back and eventually acquire almost their initial speed. For larger velocities,
the skyrmions approach each other and shrink until they become singular points
and are eventually annihilated. We describe the observed phenomena in terms of
skyrmion energetics and thus determine the regimes of the different dynamical
behaviors.
