Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The packing chromatic number of the infinite square lattice is between
  13 and 15   Using a SAT-solver on top of a partial previously-known solution we improve
the upper bound of the packing chromatic number of the infinite square lattice
from 17 to 15. We discuss the merits of SAT-solving for this kind of problem as
well as compare the performance of different encodings. Further, we improve the
lower bound from 12 to 13 again using a SAT-solver, demonstrating the
versatility of this technology for our approach.

15
The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th