Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gauging Away the Strong CP Problem   We propose a new solution to the strong-CP problem. It involves the existence
of an unbroken gauged $U(1)_X$ symmetry whose gauge boson gets a Stuckelberg
mass term by combining with a pseudoscalar field $\eta (x)$. The latter has
axion-like couplings to $F_{QCD}\wedge F_{QCD}$ so that the theta parameter may
be gauged away by a $U(1)_X$ gauge transformation. This system leads to mixed
gauge anomalies and we argue that they are cancelled by the addition of an
appropriate Wess-Zumino term, so that no SM fermions need to be charged under
$U(1)_X$. We discuss scenarios in which the above set of fields and couplings
appear. The mechanism is quite generic, but a natural possibility is that the
the $U(1)_X$ symmetry arises from bulk gauge bosons in theories with extra
dimensions or string models. We show that in certain D-brane Type-II string
models (with antisymmetric tensor field strength fluxes) higher dimensional
Chern-Simons couplings give rise to the required D=4 Wess-Zumino terms upon
compactification. In one of the possible string realizations of the mechanism
the $U(1)_X$ gauge boson comes from the Kaluza-Klein reduction of the
eleven-dimensional metric in M-theory.

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The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
1
The categories of this paper are: cs
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The categories of this paper are: adap-org
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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The categories of this paper are: math
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The categories of this paper are: atom-ph
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The categories of this paper are: supr-con
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The categories of this paper are: q-alg
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-lat
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: alg-geom