Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Vacuum Accumulation Solution to the Strong CP Problem   We suggest a solution to the strong CP problem in which there are no axions
involved. The superselection rule of the \theta-vacua is dynamically lifted in
such a way that an infinite number of vacua are accumulated within the
phenomenologically acceptable range of \theta < 10^{-9}, whereas only a
measure-zero set of vacua remains outside of this interval. The general
prediction is the existence of membranes to which the standard model gauge
fields are coupled. These branes may be light enough for being produced at the
particle accelerators in form of the resonances with a characteristic membrane
spectrum.

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The categories of this paper are: ao-sci
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The categories of this paper are: q-alg
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
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The categories of this paper are: stat
4
The categories of this paper are: cond-mat
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The categories of this paper are: chao-dyn
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The categories of this paper are: econ
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The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: comp-gas
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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: quant-ph
5
The categories of this paper are: gr-qc