Quasicrystals and their symmetries

This paper is a survey of results on symmetries of crystals and of some results on a mathematical approach to the theory of quasicrystals and their symmetries. __________ Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 10, No. 3, pp. 3–10, 2004.     

Coloring Quasicrystals with Prescribed Symmetries and Frequencies

We show how to color the tiles in a heirarchical tiling system so that the resulting system is not only repetitive (i.e., has the local isomorphism property) but has prescribed color symmetries as well. Received March 9, 1998, and in revised form August 3, 1998.     

二维八次对称准晶的断裂动力学问题

基于准晶弹性流体动力学模型,采用有限差分法研究了含Griffith裂纹八次对称准晶在不同冲击载荷下的动态响应,得到了应力、位移和应力强度因子的数值结果,讨论了不同冲击载荷对动力学行为的影响.     

Quasicrystals are sets of stable sampling

Irregular sampling and “stable sampling” of band-limited functions have been studied by H.J. Landau [H.J. Landau, Necessary density conditions for sampling and interpolation of certain entire functions, Acta Math. 117 (1967) 37–52]. We prove that quasicrystals are sets of stable sampling. To cite this article: B. Matei, Y. Meyer, C. R. Acad. Sci. Paris, Ser. I 346 (2008).     

软物质准晶三维广义流体动力学

讨论了软物质准晶三维广义流体动力学.主要是给出了已经发现的和可能发现的第一类二维软物质准晶的动力学方程组,也简单地讨论了一下它们的解,以及这些解和固体准晶解的结果的巨大差别.     

Quasicrystals,aperiodic order,and groupoid von Neumann algebras

We introduce tight binding operators for quasicrystals that are parametrized by Delone sets. These operators can be regarded in a natural operator algebra framework that encodes the long range aperiodic order. This algebraic point of view allows us to study spectral theoretic properties. In particular, the integrated density of states of the tight binding operators is related to a canonical trace on the associated von Neumann algebra. To cite this article: D. Lenz, P. Stollmann, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 1131–1136.     

Discrete Tomography of Mathematcal Quasicrystals: A Primer

This text is a report on work progress. We introduce the class of cyclotomic model sets (mathematical quasicrystals) $\Lambda \subset \mathbb{Z}[{\xi }_n]$, where $\mathbb{Z}[{\xi }_n]$ is the ring of integers in the nth cyclotomic field $\mathbb{Q}({\xi }_n)$, and discuss the corresponding decomposition, consistency and reconstruction problems of the discrete tomography of these sets. Our solution of the so-called decomposition problem also applies to the case of the square lattice ${\mathbb{Z}}^2=\mathbb{Z}[{\xi }_4]$, which corresponds to the classical setting of discrete tomography.     

软物质第二类二维准晶广义流体动力学

提出了第一类与第二类二维准晶概念.在笔者已有工作（范天佑. 软物质准晶广义流体动力学方程组[J]. 应用数学和力学, 2016,37(4): 331-344.）的基础上,对可能的7次、9次和14次对称软物质第二类二维准晶广义流体动力学进行了全面讨论,建立了它们的终态控制方程组,为软物质准晶学科的发展提供了一个数学模型,为探讨有关物理问题的时间 空间演化提供了可操作的实际可行的求解体系和分析工具,是对该工作的一个重要发展.     

软物质准晶广义流体动力学方程组

建立了软物质准晶广义流体动力学方程组,其基础为广义Langevin方程,推导方法为Poisson括号,它参考了固体准晶的广义流体动力学方程组,但是两者存在原则的不同.固体准晶的广义流体动力学方程组考虑了固体粘性与声子弹性和相位子弹性的相互作用,没有状态方程问题;软物质准晶广义流体动力学方程组考虑的是软物质流体声子与声子弹性和相位子弹性的相互作用,按物理学术语多出了一种元激发,而且必须考虑状态方程问题,这是一个新课题,又增加了难点.实际应用的结果发现,软物质准晶广义流体动力学方程组大大激活了广义流体动力学的效能,为软物质准晶学科的发展提供了一个数学模型,为探讨有关物理问题的时间-空间演化提供了可操作的实际可行的求解体系和分析工具,求解的结果令人满意.     

准晶弹性理论边值问题的可解性

通过给出准晶弹性偏微分方程组边值问题的矩阵表示去定义弱解,利用Korn不等式和函数空间理论证明了这种弱解的存在性与唯一性,从而把经典弹性理论边值问题解的存在性定理推广到准晶弹性理论上,这种理论为发展极其复杂与困难的准晶弹性的偏微分方程的边值问题的数值解提供了一个基础．     

Geometric Models for Quasicrystals II. Local Rules Under Isometries

The atomic structures of quasicrystalline materials exhibit long range order under translations. It is believed that such materials have atomic structures which approximately obey local rules restricting the location of nearby atoms. These local constraints are typically invariant under rotations, and it is of interest to establish conditions under which such local rules can nevertheless enforce order under translations in any structure that satisfies them. A set of local rules in is a finite collection of discrete sets {Y _i } containing 0, each of which is contained in the ball of radius ρ around 0 in . A set X satisfies the local rules under isometries if the ρ -neighborhood of each is isometric to an element of . This paper gives sufficient conditions on a set of local rules such that if X satisfies under isometries, then X has a weak long-range order under translations, in the sense that X is a Delone set of finite type. A set X is a Delone set of finite type if it is a Delone set whose interpoint distance set X-X is a discrete closed set. We show for each minimal Delone set of finite type X that there exists a set of local rules such that X satisfies under isometries and all other Y that satisfy under isometries are Delone sets of finite type. A set of perfect local rules (under isometries or under translations, respectively) is a set of local rules such that all structures X that satisfy are in the same local isomorphism class (under isometries or under translations, respectively). If a Delone set of finite type has a set of perfect local rules under translations, then it has a set of perfect local rules under isometries, and conversely. Received February 14, 1997, and in revised form February 14, 1998, February 19, 1998, and March 5, 1998.     

一维正方准晶沿准周期方向穿透的抛物线裂纹问题

利用广义复变函数方法研究了一维正方准晶材料中周期平面的抛物线裂纹问题,通过建立广义保角映射,将物理平面的抛物线裂纹外映射到数学平面里的单位圆内.得出了声子场和相位子场的应力分量在像平面下的复表示,并且得到了抛物线裂纹尖端的应力强度因子.并在特殊情况下,所得结果与Griffith裂纹的结果一致.     

含共圆循环对称裂纹的一维六方准晶平面应变第一基本问题

讨论了一维六方准晶在整个周期平面循环对称基本域中含一个共圆循环对称裂纹的全平面应变第一基本问题.利用复变函数方法,将弹性平衡的问题转化为唯一可解的Fredholm奇异积分方程.引入保角映射并结合裂纹共圆的特点得出了此问题的解析解.此问题的结果对工程断裂问题具有理论意义.     

Geometric Models for Quasicrystals I. Delone Sets of Finite Type

This paper studies three classes of discrete sets X in ⁿ which have a weak translational order imposed by increasingly strong restrictions on their sets of interpoint vectors X-X . A finitely generated Delone set is one such that the abelian group [X-X] generated by X-X is finitely generated, so that [X-X] is a lattice or a quasilattice. For such sets the abelian group [X] is finitely generated, and by choosing a basis of [X] one obtains a homomorphism . A Delone set of finite type is a Delone set X such that X-X is a discrete closed set. A Meyer set is a Delone set X such that X-X is a Delone set. Delone sets of finite type form a natural class for modeling quasicrystalline structures, because the property of being a Delone set of finite type is determined by ``local rules.' That is, a Delone set X is of finite type if and only if it has a finite number of neighborhoods of radius 2R , up to translation, where R is the relative denseness constant of X . Delone sets of finite type are also characterized as those finitely generated Delone sets such that the map ϕ satisfies the Lipschitz-type condition ||ϕ (x) - ϕ (x')|| < C ||x - x'|| for x, x' ∈X , where the norms || . . . || are Euclidean norms on ^s and ⁿ , respectively. Meyer sets are characterized as the subclass of Delone sets of finite type for which there is a linear map and a constant C such that ||ϕ (x) - (x)|| for all x∈X . Suppose that X is a Delone set with an inflation symmetry, which is a real number η > 1 such that . If X is a finitely generated Delone set, then η must be an algebraic integer; if X is a Delone set of finite type, then in addition all algebraic conjugates | η ' | η; and if X is a Meyer set, then all algebraic conjugates | η ' | 1. Received May 9, 1997, and in revised form March 5, 1998.     

一维六方准晶的两类周期接触问题

利用复变函数方法讨论了一维六方准晶非周期平面的两类周期接触问题,即无摩擦周期接触以及半平面粘结周期接触问题.利用Hilbert核积分公式,得到了两类周期接触问题封闭形式的解.对于无摩擦周期接触问题,给出了3种常见压头(周期直水平基底、周期直倾斜基底、周期圆基底)作用下接触应力的显式表达式;对于半平面粘结周期接触问题,给出了实际工程中常见的边界上有尖劈形周期位移情况下应力的解析表达式.当忽略相位子场的贡献时,结果与正交各向异性材料周期接触问题的相应结果一致.     

十次对称二维准晶弹性半平面问题的复变函数方法

研究了集中力作用下二维十次对称准晶半平面弹性问题的复变函数方法.首先将Stroh公式推广到二维准晶中,这里保留了Stroh公式的本质特征,在此基础上,采用推广的Stroh公式给出了应力和位移的通解,结合边界条件,获得了应力和位移的解析表达式,为实际应用奠定了理论基础.表明复变函数方法是解决十次对称二维准晶复杂弹性边值问题的有力工具.