Higher order intercommutations in cosmic string collisions.

We report the first observation of multiple intercommutation (more than two successive reconnections) of Abelian Higgs cosmic strings at ultrahigh collision speeds, and the formation of "kink trains" with up to four closely spaced left- or right-moving kinks, in the deep type-II regime 16 ≤ β ≤ 64 (where β=m(scalar)2/m(gauge)2). The minimum critical speed for double reconnection goes down from ∼0.98c at β = 1 to ∼0.86c for β = 64. The process leading to the second intercommutation changes with β: it involves an expanding loop if β ≥ 16, but only a radiation blob if 1 < β ≤ 8. Triple reconnections are generic in the loop-mediated regime for collision parameters on the boundary between single and double reconnection. For β = 16 we observe quadruple events. We comment on the effect of strongly repulsive core interactions on the small scale structure on the strings and their gravitational wave emission.