Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the computation of the spectral density of two-point functions:
  complex masses, cut rules and beyond   We present a steepest descent calculation of the Kallen-Lehmann spectral
density of two-point functions involving complex conjugate masses in Euclidean
space. This problem occurs in studies of (gauge) theories with Gribov-like
propagators. As the presence of complex masses and the use of Euclidean space
brings the theory outside of the strict validity of the Cutkosky cut rules, we
discuss an alternative method based on the Widder inversion operator of the
Stieltjes transformation. It turns out that the results coincide with those
obtained by naively applying the cut rules. We also point out the potential
usefulness of the Stieltjes (inversion) formalism when non-standard propagators
are used, in which case cut rules are not available at all.

4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
3
The categories of this paper are: physics