Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Perturbative approaches in relativistic kinetic theory and the emergence
  of first-order hydrodynamics   Hydrodynamics can be formulated in terms of a perturbative series in
derivatives of the temperature, chemical potential, and flow velocity around an
equilibrium state. Different formulations for this series have been proposed
over the years, which consequently led to the development of various
hydrodynamic theories. In this work, we discuss the relativistic
generalizations of the perturbative expansions put forward by Chapman and
Enskog, and Hilbert, using general matching conditions in kinetic theory. This
allows us to describe, in a comprehensive way, how different out-of-equilibrium
definitions for the hydrodynamic fields affect the development of the
hydrodynamic perturbative series. We provide a perturbative method for
systematically deriving the hydrodynamic formulation recently proposed by
Bemfica, Disconzi, Noronha, and Kovtun (BDNK) from relativistic kinetic theory.
The various transport coefficients that appear in BDNK (at first-order) are
explicitly computed using a new formulation of the relaxation time
approximation for the Boltzmann equation. Assuming Bjorken flow, we also
determine the hydrodynamic attractors of BDNK theory and compare the overall
hydrodynamic evolution obtained using this formulation with that generated by
the Israel-Stewart equations of motion and also kinetic theory.

17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
3
The categories of this paper are: physics
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
24
The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
18
The categories of this paper are: econ
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci