Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Initial State Summary of Hard Probes 2020   The description of the initial state of heavy ion collisions, which covers
the description of the incoming nuclei, the initial hard and soft interactions,
the resulting spatial geometry of the produced matter, as well as the dynamic
approach to a medium well described by hydrodynamics, has important
consequences for the study of hard and electromagnetic probes. I will review
new developments presented at Hard Probes 2020 that have an impact on these
aspects of our understanding of the initial state of heavy ion and smaller
system collisions.

11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol