Fractal interpolation on the Sierpinski Gasket

We prove for the Sierpinski Gasket (SG) an analogue of the fractal interpolation theorem of Barnsley. Let V₀={p₁,p₂,p₃} be the set of vertices of SG and the three contractions of the plane, of which the SG is the attractor. Fix a number n and consider the iterations uw=uw₁uw₂?uwn for any sequence w=(w₁,w₂,…,wn)∈n{1,2,3}. The union of the images of V₀ under these iterations is the set of nth stage vertices Vn of SG. Let F:Vn→R be any function. Given any numbers αw(w∈n{1,2,3}) with 0<|αw|<1, there exists a unique continuous extension of F, such that

f(uw(x))=αwf(x)+hw(x)     

关于Sierpinski垫片的一个注记

指出本刊2001年发表的“关于S ierp insk i垫片的H ausdorff测度”一文的主要结论是错误的,并给出有关讨论.     

Sierpinski Gasket格点图上的渗流模型

本文研究了Ｓｉｅｒｐｉｎｓｋｉ ｇａｓｋｅｔ上的边渗流模型。首先证明了该模型没有临界现象,进一步给出了其一个指数衰减律,进而证明了临界值的唯一性。     

Orthogonal Polynomials on the Sierpinski Gasket

The construction of a Laplacian on a class of fractals which includes the Sierpinski gasket (SG) has given rise to intensive research on analysis on fractals. For instance, a complete theory of polynomials and power series on SG has been developed by one of us and his coauthors. We build on this body of work to construct certain analogs of classical orthogonal polynomials (OP) on SG. In particular, we investigate key properties of these OP on SG, including a three-term recursion formula and the asymptotics of the coefficients appearing in this recursion. Moreover, we develop numerical tools that allow us to graph a number of these OP. Finally, we use these numerical tools to investigate the structure of the zero and the nodal sets of these polynomials.     

Extensions and their Minimizations on the Sierpinski Gasket

We study the extension problem on the Sierpinski Gasket (SG). In the first part we consider minimizing the functional \(\mathcal {E}_{\lambda }(f) = \mathcal {E}(f,f) + \lambda \int f^{2} d \mu \) with prescribed values at a finite set of points where \(\mathcal {E}\) denotes the energy (the analog of \(\int |\nabla f|^{2}\) in Euclidean space) and μ denotes the standard self-similiar measure on SG. We explicitly construct the minimizer \(f(x) = \sum _{i} c_{i} G_{\lambda }(x_{i}, x)\) for some constants c _i , where G _λ is the resolvent for λ≥0. We minimize the energy over sets in SG by calculating the explicit quadratic form \(\mathcal {E}(f)\) of the minimizer f. We consider properties of this quadratic form for arbitrary sets and then analyze some specific sets. One such set we consider is the bottom row of a graph approximation of SG. We describe both the quadratic form and a discretized form in terms of Haar functions which corresponds to the continuous result established in a previous paper. In the second part, we study a similar problem this time minimizing \(\int _{SG} |\Delta f(x)|^{2} d \mu (x)\) for general measures. In both cases, by using standard methods we show the existence and uniqueness to the minimization problem. We then study properties of the unique minimizers.     

The Finite Element Method on the Sierpinski Gasket

For certain classes of fractal differential equations on the Sierpinski gasket, built using the Kigami Laplacian, we describe how to approximate solutions using the finite element method based on piecewise harmonic or piecewise biharmonic splines. We give theoretical error estimates, and compare these with experimental data obtained using a computer implementation of the method (available at the web site http://mathlab.cit.cornell.edu/\sim gibbons). We also explain some interesting structure concerning the spectrum of the Laplacian that became apparent from the experimental data. March 29, 2000. Date revised: March 6, 2001. Date accepted: March 21, 2001.     

Isoperimetric Estimates on Sierpinski Gasket Type Fractals

For a compact Hausdorff space that is pathwise connected, we can define the connectivity dimension to be the infimum of all such that all points in can be connected by a path of Hausdorff dimension at most . We show how to compute the connectivity dimension for a class of self-similar sets in that we call point connected, meaning roughly that is generated by an iterated function system acting on a polytope such that the images of intersect at single vertices. This class includes the polygaskets, which are obtained from a regular -gon in the plane by contracting equally to all vertices, provided is not divisible by 4. (The Sierpinski gasket corresponds to .) We also provide a separate computation for the octogasket (), which is not point connected. We also show, in these examples, that , where the infimum is taken over all paths connecting and , and denotes Hausdorff measure, is equivalent to the original metric on . Given a compact subset of the plane of Hausdorff dimension and connectivity dimension , we can define the isoperimetric profile function to be the supremum of , where is a region in the plane bounded by a Jordan curve (or union of Jordan curves) entirely contained in , with . The analog of the standard isperimetric estimate is . We are particularly interested in finding the best constant and identifying the extremal domains where we have equality. We solve this problem for polygaskets with . In addition, for we find an entirely different estimate for as , since the boundary of has infinite measure. We find that the isoperimetric profile function is discontinuous, and that the extremal domains have relatively simple polygonal boundaries. We discuss briefly the properties of minimal paths for the Sierpinski gasket, and the isodiametric problem in the intrinsic metric.

     

关于Sierpinski垫片的Hausdorff测度

本文给出了 Sierpinski垫片的另一构造方法 ,并给出了它的 Hausdorff测度的精确值     

空间Sierpinski垫上的五元素正交指数系

设p_1,p_2,p_3∈Z\{0,±1},e_1,e_2,e_3是R~3上标准的单位正交基,由扩张矩阵M=diag[p_1,p_2,p_3]和数字集D={0,e_1,e_2,e_3}确定的自仿测度μM,D是支撑在空间Sierpinski垫T(M,D)上,其对应的Hilbert空间L~2(μM,D)上正交指数系的有限性与无限性问题已经解决.在有限的情形下,空间L~2(μM,D)上正交指数系基数的最佳上界为"4"的猜测还未完全解决.本文构造出了此空间上一列五元素正交指数函数系,说明上述最佳上界为"4"的猜测是错误的.     

Spectral Self-Affine Measures on the Generalized Three Sierpinski Gasket

The self-affine measure μM,Dassociated with an iterated function system{φd(x)=M~(-1)(x + d)}_(d∈D) is uniquely determined. It only depends upon an expanding matrix M and a finite digit set D. In the present paper we give some sufficient conditions for finite and infinite families of orthogonal exponentials. Such research is necessary to further understanding the non-spectral and spectral of μM,D. As an application,we show that the L~2(μM,D) space has infinite families of orthogonal exponentials on the generalized three Sierpinski gasket. We then consider the spectra of a class of self-affine measures which extends several known conclusions in a simple manner.     

p-Energy and p-Harmonic Functions on Sierpinski Gasket Type Fractals

We show that it is possible to define a notion of p-energy for functions defined on a class of fractals including the Sierpinski gasket (SG) for any value of p, 1<p<, extending the construction of Kigami for p=2, as a renormalized limit of modified p-energies on a sequence of graphs. Our proof is non-constructive, and does not settle the question of uniqueness. Based on the p-energy we may define p-harmonic functions as p-energy minimizers subject to boundary conditions, but again uniqueness is only conjectural. We present some numerical data as a complement to our results. This work is intended to pave the way for an eventual theory of p-Laplacians on fractals.     

Mean Value Property of Harmonic Functions on the Tetrahedral Sierpinski Gasket

Journal of Fourier Analysis and Applications - In this paper, we study the mean value property for both the harmonic functions and the functions in the domain of the Laplacian on the tetrahedral...     

Asymptotically One-Dimensional Diffusion on the Sierpinski Gasket and Multi-Type Branching Processes with Varying Environment

Asymptotically one-dimensional diffusions on the Sierpinski gasket constitute a one parameter family of processes with significantly different behaviour to the Brownian motion. Due to homogenization effects they behave globally like the Brownian motion, yet locally they have a preferred direction of motion. We calculate the spectral dimension for these processes and obtain short time heat kernel estimates in the Euclidean metric. The results are derived using branching process techniques, and we give estimates for the left tail of the limiting distribution for a supercritical multi-type branching process with varying environment.     

Heat Kernel Asymptotics for the Measurable Riemannian Structure on the Sierpinski Gasket

For the measurable Riemannian structure on the Sierpinski gasket introduced by Kigami, various short time asymptotics of the associated heat kernel are established, including Varadhan’s asymptotic relation, some sharp one-dimensional asymptotics at vertices, and a non-integer-dimensional on-diagonal behavior at almost every point. Moreover, it is also proved that the asymptotic order of the eigenvalues of the corresponding Laplacian is given by the Hausdorff and box-counting dimensions of the space.     

A Grain of Dust Falling Through a Sierpinski Gasket

In this paper we analyze the downward random motion of a particle in a vertical, bounded, Sierpinski gasket G, where at each layer either absorption or delays are considered. In the case of motion with absorption the explicit distribution of the position of the descending particle in the pre-gasket Gn is obtained and the limiting case of the Sierpinski gasket discussed. For the delayed downward motion we derive a representation of the random time needed to arrive at the base of Gn in terms of independent binomial random variables （containing the contribution of delays at different layers with different geometrical structures）.     

Mean Value Properties of Harmonic Functions on Sierpinski Gasket Type Fractals

In this paper, we establish an analogue of the classical mean value property for both the harmonic functions and some general functions in the domain of the Laplacian on the Sierpinski gasket. Furthermore, we extend the result to some other p.c.f. fractals with Dihedral-3 symmetry.     

On the Application of Monotonicity Methods to the Boundary Value Problems on the Sierpinski Gasket

We show that the monotonicity methods can also be applied in the fractal setting to examine existence and also existence and uniqueness. Furthermore, we investigate the continuous dependence on parameters for the problem under consideration.