Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Many-polaron problem by cluster perturbation theory   The carrier-density dependence of the photoemission spectrum of the Holstein
many-polaron model is studied using cluster perturbation theory combined with
an improved cluster diagonalization by Chebychev expansion.

19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
6
The categories of this paper are: astro-ph
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph