Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: $\mathcal{PT}$-symmetric mode-locking   Parity-time ($\mathcal{PT}$) symmetry is one of the most important
accomplishments in optics over the past decade. Here the concept of
$\mathcal{PT}$ mode-locking of a laser is introduced, in which active phase
locking of cavity axial modes is realized by asymmetric mode coupling in a
complex time crystal. $\mathcal{PT}$ mode-locking shows a transition from
single to double pulse emission as the $\mathcal{PT}$ symmetry breaking point
is crossed. The transition can show a turbulent behavior, depending on a
dimensionless modulation parameter that plays the same role as the Reynolds
number in hydrodynamic flows.

1
The categories of this paper are: cs
11
The categories of this paper are: hep-lat
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
7
The categories of this paper are: hep-th