Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Invisibility and PT-symmetry   For a general complex scattering potential defined on a real line, we show
that the equations governing invisibility of the potential are invariant under
the combined action of parity and time-reversal (PT) transformation. We
determine the PT-symmetric an well as non-PT-symmetric invisible configurations
of an easily realizable exactly solvable model that consists of a two-layer
planar slab consisting of optically active material. Our analysis shows that
although PT-symmetry is neither necessary nor sufficient for the invisibility
of a scattering potential, it plays an important role in the characterization
of the invisible configurations. A byproduct of our investigation is the
discovery of certain configurations of our model that are effectively
reflectionless in a spectral range as wide as several hundred nanometers.

37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
21
The categories of this paper are: adap-org
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int