Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Observation of topological $Z_2$ vortex fluctuations in the frustrated
  Heisenberg magnet NaCrO$_2$
19
The categories of this paper are: eess
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org