Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Problems of Perturbation Series in Non-Equilibrium Quantum Field
  Theories   In the standard framework of non-equilibrium quantum field theories, the
pinch singularities associated to multiple products of $\delta$-functions do
not cancel in a perturbative expansion unless the particle distributions are
those for a system in thermal and chemical equilibrium.

28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph