Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Control of light speed: From slow light to superluminal light   A scheme for controlling light speed from slower-than-c to faster-than-c in
an atomic system is presented in this paper. The scheme is based on far
detuning Raman effect. Two far detuning coupling fields with small frequency
difference will produce two absorptive peaks for the probe field in a $\Lambda$
structure, and an optical pump between the two ground states can change the
absorptive peaks into enhanced peaks, which makes the normal dispersion between
the two peaks change into anomalous dispersion, so the probe field can change
from slow light to superluminal propagation.

22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg