Different aspects of the strong interaction in particle collisions are studied. Most of the work is based on the Lund string fragmentation model for hadron production. A model which incorporates interference between identical bosons in the string model is presented. With this model the consequences for the Bose-Einstein effect are investigated in detail. What happens at the end of the QCD cascades is also addressed. It is shown that, with just a few reasonable assumptions, the emission of soft gluons is constrained to produce an ordered field in the form of a helix. A signature of the helix field which should survive fragmentation is presented. Inspired by the Feynman-Wilson gas analogy a partition function for the string model is derived and its properties are investigated.