Monopole-Antimonopole Scattering

We numerically study the head-on scattering of a 't Hooft-Polyakov magnetic monopole and antimonopole for a wide range of parameters. In contrast to the scattering of a $\lambda \phi^4$ kink and antikink in 1+1 dimensions, we find that the monopole and antimonopole annihilate even when scattered at relativistic velocities. If the monopole and antimonopole have a relative twist, there is a repulsive force between them and they can initially be reflected. However, in every case we have examined, the reflected monopoles remain bound and eventually annihilate. We also calculate the magnetic helicity in the aftermath of monopole-antimonopole annihilation and confirm the conversion of relative twist to magnetic helicity as discussed earlier in the electroweak case.