Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Wave emission and absorption at spectral singularities   We studied the critical dynamics of spectral singularities. The system
investigated is a coupled resonator array with a side-coupled loss (gain)
resonator. For a gain resonator, the system acts as a wave emitter at spectral
singularities. The reflection probability increased linearly over time. The
rate of increase is proportional to the width of the incident wave packet,
which served as the spectral singularity observer in the experiment. For a
lossy resonator, the system acts as a wave absorber. The emission and
absorption states at spectral singularities coalesce in a finite parity-time
(PT ) symmetric system that combined by the gain and loss structures cut from
corrresponding scattering systems at spectral singularities; in this case, the
PT -symmetric system is at an exceptional point with a 2 * 2 Jordan block. The
dynamics of the PT -symmetric system exhibit the characteristic of exceptional
points and spectral singularities.

11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
2
The categories of this paper are: math