The fundamental goal of physics is an understanding of the forces of nature in their simplest and most general terms. Yet there is much more involved than just a basic set of equations which eventually has to be solved when applied to specific problems. We have learned in recent years that the structure of the ground state of field theories (with which we are generally concerned) plays an equally funda mental role as the equations of motion themselves. Heisenberg was probably the first to recognize that the ground state, the vacuum, could acquire certain prop erties (quantum numbers) when he devised a theory of ferromagnetism. Since then, many more such examples are known in solid state physics, e. g. supercon ductivity, superfluidity, in fact all problems concerned with phase transitions of many-body systems, which are often summarized under the name synergetics. Inspired by the experimental observation that also fundamental symmetries, such as parity or chiral symmetry, may be violated in nature, it has become wide ly accepted that the same field theory may be based on different vacua. Practical ly all these different field phases have the status of more or less hypothetical models, not (yet) directly accessible to experiments. There is one magnificent ex ception and this is the change of the ground state (vacuum) of the electron-posi tron field in superstrong electric fields."

The purpose of this volume is to trace the development of the
theoretical understanding of quark-gluon plasma, both in terms of the
equation of state and thermal correlation functions and in terms of
its manifestation in high energy nuclear collisions. Who among us has
not wondered how tall a mountain is on a neutron star, what happens
when matter is heated and compressed to higher and higher densities,
what happens when an object falls into a black hole, or what happened
eons ago in the early universe? The study of quark-gluon plasma is
related in one way or another to these and other thought provoking
questions. Oftentimes the most eloquent exposition is given in the
original papers. To this end a selection is made of what are the
most important pioneering papers in this field. The early 1950s was
an era when high energy multiparticle production in cosmic ray
interactions attracted the attention of some of the brightest minds
in physics, and so it should be no surprise that the first reprinted
papers deal with the introduction of statistical models of particle
production. The quark model arose in the 1960s, while QCD as such
was recognized as the theory of the strong interactions in the
1970's. The behavior of matter at high temperatures and supranuclear
densities became of wide interest in the nuclear and particle physics
communities starting in the 1970s, which is when the concept of
quark-gluon plasma became established. The history of the field has
been traced up to the early 1990s. There are three reasons for
stopping at that point in time. First, most of the key theoretical
concepts and formalisms arose before 1993, although many of them
continue to be developed today and hopefully well into the future.
Second, papers written after 1992 are much more readily available
than those writen before due to the advent of the World Wide Web and
its electronic preprint databases and journals. Finally, in making
this collection of reprints available as hardcopy one is limited in
the number of pages, and some papers in the present selection should
have been deleted in order to make room for post-1993 papers. For the
same reason the subject focus must of necessity be limited, which
means that in this reprint collection two wide subject areas are not
addressed: the behavior of nuclear matter under extreme conditions
is not reported, nor is quark matter in neutron stars. The broad
categories into which the material has been placed, reflect the
diverse studies of quark-gluon plasma and its manifestation. They
are: phase-space models of particle production, perturbative QCD
plasma, lattice gauge theory, fluid dynamics and flow, strangeness,
heavy flavor (charm), electromagnetic signals, parton cascade and
minijets, parton energy loss and jet quenching, Hanbury Brown--Twiss
(HBT) interferometry, disoriented chiral condensates, phase
transition dynamics and cosmology, and color superconductivity. Each
chapter is prefaced by an introduction, which contains a list of
significant papers which is more complete than the reprinted papers,
though by no means exhaustive. It also contains citations to most
relevant papers published up to the date of completion of this volume
(fall 2002). It is hoped that the short reviews will help bring the
reader up to date on the latest developments. The selection of
papers cited in each chapter, and in particular the ones selected for
reprinting, is solely the responsibility of the Editors. It is based
on their best judgement and experience in this field dating back to
the mid-1970s. In order to be reprinted a paper must have been
pioneering in the sense of originality and impact on the field.
Generally they have been cited over a hundred times by other papers
published in refereed journals. The final selection was reviewed and
discussed among the Editors repeatedly. Just because a paper is not
included does not mean they do not know of it or do not have a high
regard for it. All of the papers cited or reprinted are original
research contributions. There are three other types of publications
listed. The first is a compilation of books. The second is a list
of reviews, many of which contain a significant amount of original
material. The third is a list of the proceedings of the series of
Quark Matter meetings, the primary series of international
conferences in this field that is attended by both theorists and
experimentalists.