Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: One-loop Amplitudes as BPS state sums   We review a novel method for evaluating one-loop BPS-saturated amplitudes in
string theory. Contrary to traditional techniques of unfolding the fundamental
domain F against the Narain lattice, which are only valid in certain regions of
the moduli space and which obscure the T- duality invariance of the result, we
will describe how the elliptic genus can be represented as a linear combination
of certain absolutely convergent Poincar\'e series, against which F can be
unfolded. The result can be expressed as a sum of one-loop contributions of
perturbative BPS-states in a manifestly T-duality invariant fashion, valid at
any point of (the perturbative) moduli space. Within this framework, the
singularity structure of amplitudes around points of gauge symmetry enhancement
becomes crystal clear and a series of applications is given in order to better
illustrate the power of this approach.

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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat
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The categories of this paper are: alg-geom
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The categories of this paper are: cmp-lg
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The categories of this paper are: math-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: econ
12
The categories of this paper are: nucl-th
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The categories of this paper are: supr-con
1
The categories of this paper are: cs
2
The categories of this paper are: math