Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theory of light amplification in active fishnet metamaterials   We establish a theory that traces light amplification in an active
double-fishnet metamaterial back to its microscopic origins. Based on ab initio
calculations of the light/plasmon fields we extract energy rates and conversion
efficiencies associated with gain/loss channels directly from Poynting's
theorem. We find that for the negative refactive index mode both radiative loss
and gain outweigh resistive loss by more than a factor of two, opening a broad
window of steady-state amplification (free of instabilities) accessible even
when a gain reduction close to the metal is taken into account.

2
The categories of this paper are: math
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
19
The categories of this paper are: eess