Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Equations of macroscopic electrodynamics for two-dimensional crystals   The electrodynamics of two-dimensional (2D) dielectric and conducting layers
cannot be described by such three-dimensional macroscopic quantities as the
dielectric constant $\epsilon$ or the refractive index $n$. By means of the
proper averaging of the microscopic Maxwell equations we derive general
macroscopic electrodynamic equations for 2D crystals and discuss some of their
consequences.

9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio