Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Reconstructing the thermal Green functions at real times from those at
  imaginary times   By exploiting the analyticity and boundary value properties of the thermal
Green functions that result from the KMS condition in both time and energy
complex variables, we treat the general (non-perturbative) problem of
recovering the thermal functions at real times from the corresponding functions
at imaginary times, introduced as primary objects in the Matsubara formalism.
The key property on which we rely is the fact that the Fourier transforms of
the retarded and advanced functions in the energy variable have to be the
`unique Carlsonian analytic interpolations' of the Fourier coefficients of the
imaginary-time correlator, the latter being taken at the discrete Matsubara
imaginary energies, respectively in the upper and lower half-planes. Starting
from the Fourier coefficients regarded as `data set', we then develop a method
based on the Pollaczek polynomials for constructing explicitly their analytic
interpolations.

20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom