Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theory and Numerical Modelling of Parity-Time Symmetric Structures in
  Photonics: Introduction and Grating Structures in One Dimension   A class of structures based on PT PT-symmetric Bragg gratings in the presence
of both gain and loss is studied. The basic concepts and properties of parity
and time reversal in one-dimensional structures that possess idealised material
properties are given. The impact of realistic material properties on the
behaviour of these devices is then investigated. Further extension to include
material non-linearity is used to study an innovative all-optical memory
device.

14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th