Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Effect of Choices of Boundary Conditions on the Numerical Efficiency of
  Direct Solutions of Finite Difference frequency Domain Systems with Perfectly
  Matched Layers
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess