Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: WMAP Constraints on varying $\alpha$ and the Promise of Reionization   We present up-to-date constraints on the value of the fine-structure constant
at the epoch of decoupling from the recent observations made by the Wilkinson
Microwave Anisotropy Probe (WMAP) satellite. In the framework of models we
considered, a positive (negative) variation of the value of $\alpha$ at
decoupling with respect to the present-day value is now bounded to be smaller
than 2% (6%) at 95% confidence level. We point out that the existence of an
early reionization epoch as suggested by the above measurements will, when more
accurate cosmic microwave background polarization data is available, lead to
considerably tighter constraints. The so-called `reionization bump', in
particular, will be extremely useful for this purpose. We find that constraints
on $\alpha$ can in principle only be as small as $0.1 %$ using CMB data
alone--tighter constraints will require further (non-CMB) priors.

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The categories of this paper are: comp-gas
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The categories of this paper are: supr-con
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The categories of this paper are: q-fin
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: eess
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The categories of this paper are: atom-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: ao-sci
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The categories of this paper are: q-alg
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The categories of this paper are: chem-ph
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The categories of this paper are: econ
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The categories of this paper are: cond-mat