Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observables of String Field Theory   We study gauge invariant operators of open string field theory and find a
precise correspondence with on-shell closed strings. We provide a detailed
proof of the gauge invariance of the operators and a heuristic interpretation
of their correlation functions in terms of on-shell scattering amplitudes of
closed strings. We also comment on the implications of these operators to
vacuum string field theory.

9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol