Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Thermal fluctuations propagation in the relativistic Euler regime: a
  causal appraisal   It is shown that thermal fluctuations present in a simple non-degenerate
relativistic fluid satisfy a wave equation in the Euler regime. The
characteristic propagation speeds are calculated and the classical expression
for the speed of sound is recovered at the non relativistic limit. Implications
and generalizations of this work are analyzed.

9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
6
The categories of this paper are: astro-ph
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org