charges correspond to a specific SU(3) multiplet, the tension (or energy density) in the rope is given by the second Casimir operator [@Bali:2000un]. This result is valid for an isolated rope, modifications must be expected in a situation where the rope is surrounded by other ropes or strings. Here we discuss the formation of a rope, its tension, and its eventual decay.

Rope formation {#sec:ropeformation}
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We study a situation, where a rope is formed by a group of ordinary triplet–antitriplet strings, where the net colour charge is obtained from the addition of $m$ colour triplets and $n$ antitriplets with random colours. As pointed out first in ref. [@Biro:1984], the result corresponds to a kind of random walk in colour space. A detailed discussion of this process can be found  in ref. [@Jeon:2004rk] or in [appendix [\[sec:pq-calc\]]{}]{}. Here we only present the main features essential for the later discussion.

While in SU(2) a multiplet is specified by the quantum number $j$, or its multiplicity $(2j+1)$, an SU(3) multiplet can be specified by two quantum numbers $p$ and $q$. A specific state then corresponds to $p$ coherent triplets ( all red) and $q$ coherent antitriplets (all antigreen). In addition the triplet 