Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theory of combined exciton-cyclotron resonance in a two-dimensional
  electron gas: The strong magnetic field regime   I develop a theory of combined exciton-cyclotron resonance (ExCR) in a
low-density two-dimensional electron gas in high magnetic fields. In the
presence of excess electrons an incident photon creates an exciton and
simultaneously excites one electron to higher-lying Landau levels. I derive
exact ExCR selection rules that follow from the existing dynamical symmetries,
magnetic translations and rotations about the magnetic field axis. The nature
of the final states in the ExCR is elucidated. The relation between ExCR and
shake-up processes is discussed. The double-peak ExCR structure for transitions
to the first electron Landau level is predicted.

11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph
2
The categories of this paper are: math
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
19
The categories of this paper are: eess