Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Algebra of Observables of the Closed Bosonic Nambu-Goto-String: The
  Presentation of the Algebra of Classical Observables for Light-Like
  Energy-Momentum in 3+1 Dimensions
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph
27
The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph