Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Capillary transport in low saturated sands: superfast non-linear
  diffusion model versus direct experimental observations   We have established in a pilot study, that the spreading of liquids in sandy
porous materials at low levels of saturation, typically less than ten percent
of the available void space, has very distinctive features in comparison to
that at higher saturation levels. In particular, it has been shown, on
theoretical grounds, that the spreading is controlled by a special type of
diffusional process, that its physics can be captured by an equation of the
super-fast diffusion class, and that these findings were supported by
first-of-a-kind experiments. In this paper, we take these findings to the next
level including deeper examination and exposition of the theory, an expanded
set of experiments to address scaling properties, and systematic evaluations of
the predictive performance against these experimental data, keeping in mind
also potential practical applications.

35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph