Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Speed of Sound in Hadronic Matter   We calculate the speed of sound $c_s$ in an ideal gas of resonances whose
mass spectrum is assumed to have the Hagedorn form $\rho(m) \sim
m^{-a}\exp{bm}$, which leads to singular behavior at the critical temperature
$T_c = 1/b$. With $a = 4$ the pressure and the energy density remain finite at
$T_c$, while the specific heat diverges there. As a function of the temperature
the corresponding speed of sound initially increases similarly to that of an
ideal pion gas until near $T_c$ where the resonance effects dominate causing
$c_s$ to vanish as $(T_c - T)^{1/4}$. In order to compare this result to the
physical resonance gas models, we introduce an upper cut-off M in the resonance
mass integration. Although the truncated form still decreases somewhat in the
region around $T_c$, the actual critical behavior in these models is no longer
present.

37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
8
The categories of this paper are: hep-ex
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
2
The categories of this paper are: math