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We report the first observation of multiple intercommutation (more than two successive reconnections) of cosmic strings at ultra-high collision speeds, and the formation of ``kink trains'' with up to four closely spaced left- or right-moving kinks.
- We performed a flat space numerical study of abelian Higgs cosmic string intercommutation in the type-II regime $\beta > 1$ (where $\beta = m^2_{scalar} / m^2_{gauge}$) up to $\beta = 64$, the highest value investigated to date.
- Our results confirm earlier claims that the minimum critical speed for double reconnection goes down with increasing $\beta$, from $\sim 0.98 c$ at $\beta = 1$ to $\sim 0.86 c$ for $\beta = 64$.
- Furthermore, we observe a qualitative change in the process leading to the second intercommutation: if $\beta \geq 16$ it is mediated by a loop expanding from the collision point whereas if $1 < \beta \leq 8 $ the previously reported ``loop'' is just an expanding blob of radiation which has no topological features and is absorbed by the strings.