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arXiv 1301.0664math.MGmath-phmath.MP
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具有周期约束的球形填料

Ball Packings with Periodic Constraints

Robert Connelly, Jeffrey D. Shen, Alexander D. Smith

摘要:

我们称d维欧几里得空间中的周期球填充相对于周期格周期性地(严格地)堵塞,如果球没有保持周期的非平凡运动(保持体积较小或相等的某个周期)。特别地,如果填料在其每个周期上周期性地(严格地)堵塞,则我们称其为一致周期性地(严格地)堵塞。在扩展一个著名的酒吧框架和应力条件严格堵塞后,我们证明了一个包装的周期Lambda始终严格堵塞当且仅当它是严格堵塞的Lambda和始终定期堵塞。接下来,我们扩展了晶体学中刚性单位模谱的结果,以表征子晶格上的周期性干扰。在此基础上,我们证明了m个单位球的严格阻塞填充存在100多个,并得到了其它类似的结果。一个有趣的例子表明,第一个子格上的填充是第一次定期unjumping的大小是没有限制的。最后,我们找到了一个低密度一致周期性堵塞堆积的例子δ= \frac{4 π}{6 \sqrt{3} + 11} + ε~ 0.59,其中ε是一个任意小的正数.文中还对张拉整体框架中密切相关的周期无穷小刚度和仿射无穷小刚度概念进行了阐述。

英文摘要:

We call a periodic ball packing in d-dimensional Euclidean space periodically (strictly) jammed with respect to a period lattice if there are no nontrivial motions of the balls that preserve the period (that maintain some period with smaller or equal volume). In particular, we call a packing consistently periodically (strictly) jammed if it is periodically (strictly) jammed on every one of its periods. After extending a well-known bar framework and stress condition to strict jamming, we prove that a packing with period Lambda is consistently strictly jammed if and only if it is strictly jammed with respect to Lambda and consistently periodically jammed. We next extend a result about rigid unit mode spectra in crystallography to characterize periodic jamming on sublattices. After that, we prove that there are finitely many strictly jammed packings of m unit balls and other similar results. An interesting example shows that the size of the first sublattice on which a packing is first periodically unjammed is not bounded. Finally, we find an example of a consistently periodically jammed packing of low density δ= \frac{4 π}{6 \sqrt{3} + 11} + ε~ 0.59, where εis an arbitrarily small positive number. Throughout the paper, the statements for the closely related notions of periodic infinitesimal rigidity and affine infinitesimal rigidity for tensegrity frameworks are also given.

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