Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Particle correlations and evidence for dark state condensation in a cold
  dipolar exciton fluid   In this paper we show experimental evidence of a few correlation regimes of a
cold dipolar exciton fluid, created optically in a semiconductor bilayer
heterostructure. In the higher temperature regime, the average interaction
energy between the particles shows a surprising temperature dependence which is
an evidence for correlations beyond the mean field model. At a lower
temperature, there is a sharp increase in the interaction energy of optically
active excitons, accompanied by a strong reduction in their apparent
population. This is an evidence for a sharp macroscopic transition to a dark
state as was suggested theoretically.

34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
24
The categories of this paper are: dg-ga
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The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
36
The categories of this paper are: cmp-lg