PUB - Publikationen an der Universität Bielefeld

In the latter half of the last century, it became evident that there existsan ever increasing number of different states of the so-called elementaryparticles. The usual reductionist approach to this problem was to search for asimpler infrastructure, culminating in the formulation of the quark model andquantum chromodynamics. In a complementary, completely novel approach, Hagedornsuggested that the mass distribution of the produced particles follows aself-similar composition pattern, predicting an unbounded number of states ofincreasing mass. He then concluded that such a growth would lead to a limitingtemperature for strongly interacting matter. We discuss the conceptual basisfor this approach, its relation to critical behavior, and its subsequentapplications in different areas of high energy physics.