Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Non-reflecting permittivity profiles and the spatial Kramers-Kronig
  relations   We show that if the permittivity profile of a planar dielectric medium is an
analytic function in the upper (lower) half complex position plane then it
won't reflect radiation from the left (right), whatever the angle of incidence.
Consequently, using the spatial Kramers-Kronig relations one can derive a real
part of a permittivity profile from some given imaginary part (or vice versa),
such that the reflection is guaranteed to be zero. This result is valid for
both scalar and vector wave theories, and may have relevance for efficiently
absorbing radiation, or reducing reflection from bodies.

37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
1
The categories of this paper are: cs
17
The categories of this paper are: q-fin
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat