论文标题
对称刚性框架的商图
Quotient graphs of symmetrically rigid frameworks
论文作者
论文摘要
组合刚性理论中的一个自然问题涉及确定$ \ Mathbb {r}^d $中的酒吧框架的刚性或灵活性,该框架接受了一些非平凡的对称性。当$ d = 2 $时,就有有关此主题的大量文献。特别是,使用适当的组标记的商图的组合结构,典型的是对组的对称图并分析对称性(但其他框架)的刚度。但是,在反映通用刚度的情况下,当$ d \ geq 3 $时,几乎不知道合并。然而,在周期性的情况下,硼谷和streinu的关键结果是何时可以将商图提起到$ \ mathbb {r}^d $中的刚性周期性框架时。我们在$ \ mathbb {r}^d $中开发了对称框架的类似理论。获得的结果适用于所有有限和无限的二维点组,然后在任意维度上涉及各种无限点基团,足够大的有限组以及包含翻译和旋转的组。对于有限组的情况,我们还得出了有关将组标签分配给商图的概率的结果,因此在$ \ mathbb {r}^d $中,所得的升力在对称上是刚性的。
A natural problem in combinatorial rigidity theory concerns the determination of the rigidity or flexibility of bar-joint frameworks in $\mathbb{R}^d$ that admit some non-trivial symmetry. When $d=2$ there is a large literature on this topic. In particular, it is typical to quotient the symmetric graph by the group and analyse the rigidity of symmetric, but otherwise generic frameworks, using the combinatorial structure of the appropriate group-labelled quotient graph. However, mirroring the situation for generic rigidity, little is known combinatorially when $d\geq 3$. Nevertheless in the periodic case, a key result of Borcea and Streinu characterises when a quotient graph can be lifted to a rigid periodic framework in $\mathbb{R}^d$. We develop an analogous theory for symmetric frameworks in $\mathbb{R}^d$. The results obtained apply to all finite and infinite 2-dimensional point groups, and then in arbitrary dimension they concern a wide range of infinite point groups, sufficiently large finite groups and groups containing translations and rotations. For the case of finite groups we also derive results concerning the probability of assigning group labels to a quotient graph so that the resulting lift is symmetrically rigid in $\mathbb{R}^d$.