Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Renormalization Group Approach to the Problem of Flow Through Irregular
  Packed Beds   We have calculated the asymptotics of Green's function of the differential
equation of nonlinear diffusion in the microscopic range with strong porosity
fluctuations in the problem of flow through irregular packed beds for arbitrary
space dimension and arbitrary covariance of porosity fluctuations.

36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph