Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Recursive Green's function approach to Feenberg perturbation theory   We propose a new procedure by using the recursive Green's functions which
remove all the repetition terms from the time-independent perturbation series
for finite-level quantum systems. These Green's functions are introduced as a
generalization of the Brillouin-Wigner perturbation theory and the calculations
of their diagonal elements can naturally give the effective propagators which
are equal to the ones in the Feenberg perturbation theory.

27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an