Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theoretical proposal for the experimental realisation of a monochromatic
  electromagnetic knot   We propose an antenna designed to generate monochromatic electromagnetic
knots and other "unusual electromagnetic disturbances" in the microwave domain.
Our antenna is a spherical array of radiating dipolar elements configured to
approximate the desired electromagnetic field near its centre. We show
numerically that a specific embodiment of the antenna with a radius of 61.2 cm
and only 20 element pairs driven at a frequency of 2.45 GHz can yield linked
and torus-knotted electric and magnetic field lines approximating those of an
"electromagnetic tangle": a monochromatic electromagnetic knot closely related
to the well-known Ra\~nada-Hopf type electromagnetic knots but simpler in its
construction. The antenna could be used to locally excite plasmas.

22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom