240 research outputs found
Ninth and Tenth Order Virial Coefficients for Hard Spheres in D Dimensions
We evaluate the virial coefficients B_k for k<=10 for hard spheres in
dimensions D=2,...,8. Virial coefficients with k even are found to be negative
when D>=5. This provides strong evidence that the leading singularity for the
virial series lies away from the positive real axis when D>=5. Further analysis
provides evidence that negative virial coefficients will be seen for some k>10
for D=4, and there is a distinct possibility that negative virial coefficients
will also eventually occur for D=3.Comment: 33 pages, 12 figure
Linking Rigid Bodies Symmetrically
The mathematical theory of rigidity of body-bar and body-hinge frameworks
provides a useful tool for analyzing the rigidity and flexibility of many
articulated structures appearing in engineering, robotics and biochemistry. In
this paper we develop a symmetric extension of this theory which permits a
rigidity analysis of body-bar and body-hinge structures with point group
symmetries. The infinitesimal rigidity of body-bar frameworks can naturally be
formulated in the language of the exterior (or Grassmann) algebra. Using this
algebraic formulation, we derive symmetry-adapted rigidity matrices to analyze
the infinitesimal rigidity of body-bar frameworks with Abelian point group
symmetries in an arbitrary dimension. In particular, from the patterns of these
new matrices, we derive combinatorial characterizations of infinitesimally
rigid body-bar frameworks which are generic with respect to a point group of
the form .
Our characterizations are given in terms of packings of bases of signed-graphic
matroids on quotient graphs. Finally, we also extend our methods and results to
body-hinge frameworks with Abelian point group symmetries in an arbitrary
dimension. As special cases of these results, we obtain combinatorial
characterizations of infinitesimally rigid body-hinge frameworks with
or symmetry - the most common symmetry groups
found in proteins.Comment: arXiv:1308.6380 version 1 was split into two papers. The version 2 of
arXiv:1308.6380 consists of Sections 1 - 6 of the version 1. This paper is
based on the second part of the version 1 (Sections 7 and 8
- …