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We consider planar bar-and-joint frameworks with discrete point group
symmetry in which the joint positions are as generic as possible
subject to the symmetry constraint.
We provide combinatorial characterizations for
symmetry-forced rigidity of such structures with cyclic or odd-order dihedral
symmetry, unifying and extending previous work on this subject.
We also explore the matroidal background of our results and
show that the matroids induced by the row independence of the
orbit matrices of the symmetric frameworks are isomorphic to
gain sparsity matroids defined on the quotient graph
of the framework, whose edges are labeled by elements of the
corresponding symmetry group.
The proofs are based on new Henneberg type inductive constructions
of the gain graphs that correspond to the bases of the matroids
in question, which can also be seen as symmetry preserving
graph operations in the original graph.
Bibtex entry:
AUTHOR | = | {Jord{\'a}n, Tibor and Kaszanitzky, Vikt{\'o}ria and Tanigawa, Shin-ichi}, |
TITLE | = | {Gain-sparsity and Symmetry-forced Rigidity in the Plane}, |
NOTE | = | {{\tt egres.elte.hu}}, |
INSTITUTION | = | {Egerv{\'a}ry Research Group, Budapest}, |
YEAR | = | {2012}, |
NUMBER | = | {TR-2012-17} |