Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultrarelativistic heavy ion collisions: the first billion seconds   I first review the early history of the ultrarelativistic heavy ion program,
starting with the 1974 Bear Mountain Workshop, and the 1983 Aurora meeting of
the U.S. Nuclear Science Committee, just one billion seconds ago, which laid
out the initial science goals of an ultrarelativistic collider. The primary
goal, to discover the properties of nuclear matter at the highest energy
densities, included finding new states of matter -- the quark-gluon plasma
primarily -- and to use collisions to open a new window on related problems of
matter in cosmology, neutron stars, supernovae, and elsewhere. To bring out how
the study of heavy ions and hot, dense matter in QCD has been fulfilling these
goals. I concentrate on a few topics, the phase diagram of matter in QCD, and
connections of heavy ion physics to cold atoms, cosmology, and neutron stars.

36
The categories of this paper are: cmp-lg
6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio