Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Angular distribution of photoluminescence as a probe of Bose
  Condensation of trapped excitons   Recent experiments on two-dimensional exciton systems have shown the excitons
collect in shallow in-plane traps. We find that Bose condensation in a trap
results in a dramatic change of the exciton photoluminescence (PL) angular
distribution. The long-range coherence of the condensed state gives rise to a
sharply focussed peak of radiation in the direction normal to the plane. By
comparing the PL profile with and without Bose Condensation we provide a simple
diagnostic for the existence of a Bose condensate. The PL peak has strong
temperature dependence due to the thermal order parameter phase fluctuations
across the system. The angular PL distribution can also be used for imaging
vortices in the trapped condensate. Vortex phase spatial variation leads to
destructive interference of PL radiation in certain directions, creating nodes
in the PL distribution that imprint the vortex configuration.

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The categories of this paper are: q-alg
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The categories of this paper are: q-fin
3
The categories of this paper are: physics
27
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: chem-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
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The categories of this paper are: eess
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-lat
18
The categories of this paper are: econ