Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electromagnetic fields and potentials generated by massless charged
  particles   We provide for the first time the exact solution of Maxwell's equations for a
massless charged particle moving on a generic trajectory at the speed of light.
In particular we furnish explicit expressions for the vector potential and the
electromagnetic field, which were both previously unknown, finding that they
entail different physical features for bounded and unbounded trajectories. With
respect to the standard Lienard-Wiechert field the electromagnetic field
acquires singular delta-like contributions whose support and dimensionality
depend crucially on whether the motion is a) linear, b) accelerated unbounded,
c) accelerated bounded. In the first two cases the particle generates a planar
shock-wave-like electromagnetic field traveling along a straight line. In the
second and third cases the field acquires, in addition, a delta-like
contribution supported on a physical singularity-string attached to the
particle. For generic accelerated motions a genuine radiation field is also
present, represented by a regular principal-part type distribution diverging on
the same singularity-string.

13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg