Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Investigating the domain of validity of the Gubser solution to the
  Boltzmann equation   We study the evolution of the one particle distribution function that solves
exactly the relativistic Boltzmann equation within the relaxation time
approximation for a conformal system undergoing simultaneously azimuthally
symmetric transverse and boost-invariant longitudinal expansion. We show, for
arbitrary values of the shear viscosity to entropy density ratio, that the
distribution function can become negative in certain kinematic regions of the
available phase space depending on the boundary conditions. For thermal
equilibrium initial conditions, we determine numerically the physical boundary
in phase space where the distribution function is always positive definite. The
requirement of positivity of this particular exact solution restricts its
domain of validity, and it imposes physical constraints on its applicability.

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The categories of this paper are: cs
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
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The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
2
The categories of this paper are: math