assumption that a confined colour field between a quark and an antiquark is compressed to a linear flux tube, similar to a vortex line in a superconductor. When the string is stretched between separated colour charges, it can break by the production of $q\bar{q}$ pairs [@Casher:1978wy; @Andersson:1980vj; @Gurvich:1979nq; @Glendenning:1983qq] in a process similar to the production of $e^+e^-$ pairs in a homogeneous electric field [@Schwinger:1951nm]. As demonstrated in ref. [@Brezin:1970xf], this can be interpreted as the effect of a quantum-mechanical tunneling process. In the Lund model the dynamical motion of the flux tube is approximated by an infinitely thin *massless relativistic string*, and gluons are identified with transverse excitations on such a string [@Andersson:1979ij], which also has the effect that the model is infrared stable,  insensitive to soft or collinear gluons.

It was early observed that when the string hadronization model is tuned to LEP data, it slightly underestimates the production of strange particles in hadronic collisions [@Alner:1985ra]. Similarly in DIS, the LEP tune works well in the current fragmentation region (in the Breit frame), while in the proton fragmentation end, one again observes an enhanced strange quark fraction [@Aaron:2008ck]. This effect is enhanced in data from LHC, where a 