Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optimal $2$-D $(n\times m,3,2,1)$-optical orthogonal codes and related
  equi-difference conflict avoiding codes   This paper focuses on constructions for optimal $2$-D $(n\times
m,3,2,1)$-optical orthogonal codes with $m\equiv 0\ ({\rm mod}\ 4)$. An upper
bound on the size of such codes is established. It relies heavily on the size
of optimal equi-difference $1$-D $(m,3,2,1)$-optical orthogonal codes, which is
closely related to optimal equi-difference conflict avoiding codes with weight
$3$. The exact number of codewords of an optimal $2$-D $(n\times
m,3,2,1)$-optical orthogonal code is determined for $n=1,2$, $m\equiv 0
\pmod{4}$, and $n\equiv 0 \pmod{3}$, $m\equiv 8 \pmod{16}$ or $m\equiv 32
\pmod{64}$ or $m\equiv 4,20 \pmod{48}$.

4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
3
The categories of this paper are: physics
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
7
The categories of this paper are: hep-th
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph