Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the mass of the world-sheet `axion' in SU(N) gauge theories in 3+1
  dimensions   There is numerical evidence that the world sheet action of the confining flux
tube in D=3+1 SU(N) gauge theories contains a massive excitation with 0-
quantum numbers whose mass shows some decrease as one goes from SU(3) to SU(5).
It has furthermore been shown that this particle is naturally described as
arising from a topological interaction term in the world-sheet action, so that
one can describe it as being `axion'-like. Recently it has been pointed out
that if the mass of this `axion' vanishes as N -> oo then it becomes possible
for the world sheet theory to be integrable in the planar limit. In this paper
we perform lattice calculations of this `axion' mass from SU(2) to SU(12),
which allows us to make a controlled extrapolation to N=oo and so test this
interesting possibility. We find that the `axion' does not in fact become
massless as N -> oo. So if the theory is to possess planar integrability then
it must be some other world sheet excitation that becomes massless in the
planar limit.

26
The categories of this paper are: bayes-an
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin