Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Inversionless amplification and laser-induced transparency at the
  discrete transitions and the transitions to continuum   The effects of coherence of quantum transitions and the interference of
resonant nonlinear optical processes on the spectra of absorption,
amplification, and nonlinear-optical generation are considered. The most
favorable conditions are discussed for the inversionless amplification,
resonant refraction in the absence of absorption and for resonant enhancement
of nonlinear-optical generation at the discrete transitions and the transitions
to continuum.

28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio