Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Edwards entropy and compactivity in a model of granular matter   Formulating a statistical mechanics for granular matter remains a significant
challenge, in part, due to the difficulty associated with a complete
characterization of the systems under study. We present a fully characterized
model of a granular material consisting of $N$ two-dimensional, frictionless,
hard discs, confined between hard walls, including a complete enumeration of
all possible jammed structures. We show the properties of the jammed packings
are independent of the distribution of defects within the system and that all
the packings are isostatic. This suggests the assumption of equal probability
for states of equal volume, which provides one possible way of constructing the
equivalent of a microcanonical ensemble, is likely to be vaild for our model.
An application of the second law of thermodynamics involving two subsystems in
contact shows that the expected spontaneous equilibration of defects between
the two is accompanied by an increase in entropy and that the equilibirum,
obtained by entropy maximization, is characterized by the equality of
compactivities. Finally, we explore the properties of the equivalent to the
canonical ensemble for this system.

29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
6
The categories of this paper are: astro-ph
7
The categories of this paper are: hep-th
14
The categories of this paper are: math-ph