Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Reverse Brazil Nut Problem: Competition between Percolation and
  Condensation   In the Brazil nut problem (BNP), hard spheres with larger diameters rise to
the top. There are various explanations (percolation, reorganization,
convection), but a broad understanding or control of this effect is by no means
acheived. A theory is presented for the crossover from the BNP to the reverse
Brazil nut problem (RBNP) based on a competition between the percolation effect
and the condensation of hard spheres. The crossover condition is determined,
and the theoretical predictions are compared to Molecular Dynamics simulations
in two and three dimensions.

25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
6
The categories of this paper are: astro-ph
21
The categories of this paper are: adap-org
1
The categories of this paper are: cs
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The categories of this paper are: math-ph
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc