Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Three-body forces from a classical nonlinear field   Forces in the systems of two opposite sign and three identical charges
coupled to the dynamical scalar field of the signum-Gordon model are
investigated. Three-body force is present, and the exact formula for it is
found. Flipping the sign of one of the two charges changes not only the sign
but also the magnitude of the force. Both effects are due to nonlinearity of
the field equation.

8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat