Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Accuracy Directly Controlled Fast Direct Solutions of General ${\cal
  H}^2$-Matrices and Its Application to Electrically Large
  Integral-Equation-Based Electromagnetic Analysis
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
25
The categories of this paper are: patt-sol
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph