Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Compaction and mobility in randomly agitated granular assemblies   We study the compaction and mobility properties of a dense granular material
under weak random vibration. By putting in direct contact millimetric glass
beads with piezoelectric transducers we manage to inject energy to the system
in a disordered manner with accelerations much smaller than gravity, resulting
in a slow compaction dynamics and no convection. We characterize the mobility
inside the medium by pulling through it an intruder grain at constant velocity.
We present an extensive study of the relation between drag force and velocity
for different vibration conditions and sizes of the intruder.

19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th