Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theory of magnetophonon resonance in 2D electron gas in tilted magnetic
  field   A theory of magnetophonon resonance in quantum wells in a magnetic field
tilted to the perpendicular to 2DEG is developed. The resonance is due to the
resonant interaction of 2D conduction electrons with the longitudinal optic
phonons. The electrons are assumed to be nondegenerate. The angular dependence
of the resonant maxima is investigated. The sharpness of the angular
dependence, as well as the existence of double resonances, i.e. two resonant
peaks for each resonance number is explained. A relation between the electron
concentration dependence of the resonance amplitude in the perpendicular
magnetic field and the angular dependence in the tilted field is analyzed.
Investigation of the angular dependence can give information concerning the
electron spectra, optic phonon and electron damping and the electron-phonon
interaction in quantum wells.

2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org