Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Luminescence and absorption in short period superlattices   This paper applies analytical approximations for the luminescence of short
period semiconductor superlattices and analyses the low density regime,
demonstrating that the theory clearly connects with low density absorption with
ratios of oscillator strengths of bound and continuum states as expected from
the Elliott formula. A numerical study illustrates in detail the bleaching of
higher order bound state. The analytical expressions have potential for
systematic studies of controlled excitonic pathways characterized by THz
responses.

7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
19
The categories of this paper are: eess