Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cutting rules on a cylinder: a bottom-up approach to quantum kinetic
  theory for the early universe   Nonequilibrium quantum field theory is often used to derive an approximation
for the evolution of number densities and asymmetries in astroparticle models
when a more precise treatment of quantum thermal effects is required. This work
presents an alternative framework using the zero-temperature quantum field
theory, $S$-matrix unitarity, and classical Boltzmann equation as starting
points leading to a set of rules for calculations of thermal corrections to
reaction rates. Statistical factors due to on-shell intermediate states are
obtained from the cuts of forward diagrams with multiple spectator lines. It
turns out that it is equivalent to cutting closed diagrams on a cylindrical
surface.

35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
3
The categories of this paper are: physics
1
The categories of this paper are: cs
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex