Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A short introduction to heavy-ion physics   Heavy-ion collisions provide the only laboratory tests of relativistic
quantum field theory at finite temperature. Understanding these is a necessary
step in understanding the origins of our universe. These lectures introduce the
subject to experimental particle physicists, in the hope that they will be
useful to others as well. The phase diagram of QCD is briefly touched upon.
Kinematic variables which arise in the collisions of heavy-ions beyond those in
the collisions of protons or electrons are introduced. Finally, a few of the
signals studied in heavy-ion collisions, and the kind of physics questions
which they open up are discussed.

23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
14
The categories of this paper are: math-ph
3
The categories of this paper are: physics
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio