Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: What is the $i\varepsilon$ for the S-matrix?
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
6
The categories of this paper are: astro-ph
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci