Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamical equations for time-ordered Green's functions: from the Keldysh
  time-loop contour to equilibrium at finite and zero temperature   We study the dynamical equation of the time-ordered Green's function at
finite temperature. We show that the time-ordered Green's function obeys a
conventional Dyson equation only at equilibrium and in the limit of
zero-temperature. In all other cases, i.e. finite-temperature at equilibrium or
non-equilibrium, the time-ordered Green's function obeys instead a modified
Dyson equation. The derivation of this result is obtained from the general
formalism of the non-equilibrium Green's functions on the Keldysh time-loop
contour. At equilibrium, our result is fully consistent with the Matsubara
temperature Green's function formalism and also justifies rigorously the
correction terms introduced in an ad hoc way with Hedin and Lundqvist. Our
results show that one should use the appropriate dynamical equation for the
time-ordered Green's function when working beyond the equilibrium
zero-temperature limit.

13
The categories of this paper are: quant-ph
17
The categories of this paper are: q-fin
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
2
The categories of this paper are: math