Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Scattering and absorption of gravitational plane waves by rotating black
  holes   This is a study of the scattering and absorption of planar gravitational
waves by a Kerr black hole in vacuum. We apply the partial wave method to
compute cross sections for the special case of radiation incident along the
rotation axis. A catalogue of numerically-accurate cross sections is presented,
for a range of incident wavelengths $M\omega \le 4$ and rotation rates $a \le
0.999M$. Three effects are studied in detail: polarization, helicity-reversal
and glory scattering. First, a new approximation to the polarization in the
long-wavelength limit is derived. We show that black hole rotation
distinguishes between co- and counter-rotating wave helicities, leading to a
term in the cross section proportional to $a\omega$. Second, we confirm that
helicity is not conserved by the scattering process, and show that
superradiance amplifies the effect. For certain wavelengths, the back-scattered
flux is enhanced by as much as $\sim 35$ times for a rapidly-rotating hole
(e.g. for $a = 0.999M$ at $M\omega = 0.945$). Third, we observe regular glory
and spiral scattering peaks in the numerically-determined cross sections. We
show that the angular width and intensity of the peaks may be estimated via a
semi-classical approximation. We conclude with a discussion of the observable
implications of our results.

21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th