Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A concise introduction to Colombeau generalized functions and their
  applications in classical electrodynamics   The objective of this introduction to Colombeau algebras of
generalized-functions (in which distributions can be freely multiplied) is to
explain in elementary terms the essential concepts necessary for their
application to basic non-linear problems in classical physics.
  Examples are given in hydrodynamics and electrodynamics. The problem of the
self-energy of a point electric charge is worked out in detail: The Coulomb
potential and field are defined as Colombeau generalized-functions, and
integrals of nonlinear expressions corresponding to products of distributions
(such as the square of the Coulomb field and the square of the delta-function)
are calculated.
  Finally, the methods introduced in Eur. J. Phys. /28/ (2007) 267-275,
1021-1042, and 1241, to deal with point-like singularities in classical
electrodynamics are confirmed.

10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
5
The categories of this paper are: gr-qc
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The categories of this paper are: hep-lat
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The categories of this paper are: q-fin