Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A model of interband radiative transitions   We consider a simple model which is a caricature of a crystal interacting
with a radiation field. The model has two bands of continuous spectrum and the
particle can pass from the upper one to the lower by radiating a photon, the
coupling between the excited and deexcited states being of a Friedrichs type.
Under suitable regularity and analyticity assumptions we find the continued
resolvent and show that for weak enough coupling it has a curve-type
singularity in the lower halfplane which is a deformation of the upper-band
spectral cut. We then find a formula for the decay amplitude and show that for
a fixed energy it is approximately exponential at intermediate times, while the
tail has a power-like behaviour.

18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
36
The categories of this paper are: cmp-lg