Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: A Penalty-free Infeasible Approach for a Class of Nonsmooth Optimization
  Problems over the Stiefel Manifold
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ