Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fermion propagators in space-time   The one- and the two-particle propagators for an infinite non-interacting
Fermi system are studied as functions of space-time coordinates. Their
behaviour at the origin and in the asymptotic region is discussed, as is their
scaling in the Fermi momentum. Both propagators are shown to have a divergence
at equal times. The impact of the interaction among the fermions on their
momentum distribution, on their pair correlation function and, hence, on the
Coulomb sum rule is explored using a phenomenological model. Finally the
problem of how the confinement is reflected in the momentum distribution of the
system's constituents is briefly addressed.

18
The categories of this paper are: econ
19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
3
The categories of this paper are: physics
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
31
The categories of this paper are: ao-sci
24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con