Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlinear Gravitons, Null Geodesics, and Holomorphic Disks   We develop a global twistor correspondence for pseudo-Riemannian conformal
structures of signature (++--) with self-dual Weyl curvature. Near the
conformal class of the standard indefinite product metric on S^2 x S^2, there
is an infinite-dimensional moduli space of such conformal structures, and each
of these has the surprising global property that its null geodesics are all
periodic. Each such conformal structure arises from a family of holomorphic
disks in CP_3 with boundary on some totally real embedding of RP^3 into CP_3.
An interesting sub-class of these conformal structures are represented by
scalar-flat indefinite K\"ahler metrics, and our methods give particularly
sharp results in this more restrictive setting.

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The categories of this paper are: mtrl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: physics
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The categories of this paper are: alg-geom
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-bio
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The categories of this paper are: cond-mat
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The categories of this paper are: econ
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: ao-sci
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: bayes-an
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The categories of this paper are: acc-phys
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The categories of this paper are: atom-ph