Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On retardation, radiation and Li\'enard-Wiechert type potentials in
  electrodynamics and elastodynamics   The aim of this paper is to investigate the fundamental problems of
retardation and radiation caused by non-uniformly moving point sources using
the theories of electrodynamics and elastodynamics. This paper investigates and
compares the retarded electromagnetic fields and the retarded elastodynamic
fields. For the non-uniform motion of a general point source, the
Li\'enard-Wiechert type potentials and the radiation and nonradiation fields
are derived for a point charge and for a point force.

9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph