Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: H theorem for contact forces in granular materials   A maximum entropy theorem is developed and tested for granular contact
forces. Although it is idealized, describing two dimensional packings of round,
rigid, frictionless, cohesionless disks with coordination number Z=4, it
appears to describe a central part of the physics present in the more general
cases. The theorem does not make the strong claims of Edwards' hypothesis, nor
does it rely upon Edwards' hypothesis at any point. Instead, it begins solely
from the physical assumption that closed loops of grains are unable to impose
strong force correlations around the loop. This statement is shown to be a
generalization of Boltzmann's Assumption of Molecular Chaos (his
\textit{stosszahlansatz}), allowing for the extra symmetries of granular stress
propagation compared to the more limited symmetries of momentum propagation in
a thermodynamic system. The theorem that follows from this is similar to
Boltzmann's $H$ theorem and is presented as an alternative to Edwards'
hypothesis for explaining some granular phenomena. It identifies a very
interesting feature of granular packings: if the generalized
\textit{stosszahlansatz} is correct, then the bulk of homogeneous granular
packings must satisfy a maximum entropy condition simply by virtue of being
stable, without any exploration of phase space required. This leads to an
independent derivation of the contact force statistics, and these predictions
have been compared to numerical simulation data in the isotropic case. The good
agreement implies that the generalized \textit{stosszahlansatz} is indeed
accurate at least for the isotropic state of the idealized case studied here,
and that it is the reductionist explanation for contact force statistics in
this case.

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The categories of this paper are: comp-gas
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: eess
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The categories of this paper are: nlin
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The categories of this paper are: cs
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The categories of this paper are: supr-con
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The categories of this paper are: solv-int
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The categories of this paper are: quant-ph
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The categories of this paper are: stat
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The categories of this paper are: atom-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: mtrl-th