Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sub-nanometer flattening of a 45-cm long, 45-actuator x-ray deformable
  mirror   We have built a 45-cm long x-ray deformable mirror of super-polished
single-crystal silicon that has 45 actuators along the tangential axis. After
assembly the surface height error was 19 nm rms. With use of high-precision
visible-light metrology and precise control algorithms, we have actuated the
x-ray deformable mirror and flattened its entire surface to 0.7 nm rms
controllable figure error. This is, to our knowledge, the first sub-nanometer
active flattening of a substrate longer than 15 cm.

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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: acc-phys
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The categories of this paper are: alg-geom
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The categories of this paper are: math
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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: nucl-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: math-ph
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The categories of this paper are: funct-an
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The categories of this paper are: ao-sci
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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: plasm-ph