Fractals and Number Systems in Real Quadratic Number Fields

In this paper we compute the box counting dimension of sets, that are related to number systems in real quadratic number fields. The sets under discussion are so-called graph-directed self affine sets. Contrary to the case of self similar sets, for self affine sets there does not exist a general theory for the determination of the box counting dimension. Thus we are forced to construct the covers, needed for its calculation, directly. This revised version was published online in July 2006 with corrections to the Cover Date.     

Revisiting the box counting algorithm for the correlation dimension analysis of hyperchaotic time series

We undertake the correlation dimension analysis of hyperchaotic time series using the box counting algorithm. We show that the conventional box counting scheme is inadequate for the accurate computation of correlation dimension (D₂) of a hyperchaotic attractor and propose a modified scheme which is automated and gives better convergence of D₂ with respect to the number of data points. The scheme is first tested using the time series from standard chaotic systems, pure noise and data added with noise. It is then applied on the time series from three standard hyperchaotic systems for computing D₂. Our analysis clearly reveals that a second scaling region appears at lower values of box size as the system makes a transition into the hyperchaotic phase. This, in turn, suggests that correlation dimension analysis can also give information regarding chaos-hyperchaos transition.     

The Box counting Dimension of Invariant Sets for Iterated Function Systems

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Dimensions for random self–conformal sets

A set is called regular if its Hausdorff dimension and upper box–counting dimension coincide. In this paper, we prove that the random self–conformal set is regular almost surely. Also we determine the dimensions for a class of random self–conformal sets.     

Upper bounds for dominant dimensions of gendo-symmetric algebras

The famous Nakayama conjecture states that the dominant dimension of a non-selfinjective finite dimensional algebra is finite. Yamagata (Frobenius algebras handbook of algebra, vol 1. Elsevier/North-Holland, Amsterdam, pp 841–887, 1996) stated the stronger conjecture that the dominant dimension of a non-selfinjective finite dimensional algebra is bounded by a function depending on the number of simple modules of that algebra. With a view towards those conjectures, new bounds on dominant dimensions seem desirable. We give a new approach to bounds on the dominant dimension of gendo-symmetric algebras via counting non-isomorphic indecomposable summands of rigid modules in the module category of those algebras. On the other hand, by Mueller’s theorem, the calculation of dominant dimensions is directly related to the calculation of certain Ext-groups. Motivated by this connection we also give new results for showing the non-vanishing of \(Ext^{1}(M,M)\) for certain modules in local symmetric algebras, which specializes to show that blocks of category \(\mathcal {O}\) and 1-quasi-hereditary algebras with a special duality have dominant dimension exactly 2.     

Bounds on the regularity and projective dimension of ideals associated to graphs

In this paper, we give new upper bounds on the regularity of edge ideals whose resolutions are k-step linear; surprisingly, the bounds are logarithmic in the number of variables. We also give various bounds for the projective dimension of such ideals, generalizing other recent results. By Alexander duality, our results also apply to unmixed square-free monomial ideals of codimension two. We also discuss and connect these results to more classical topics in commutative algebra.     

填充维数的一个等价定义

本文研究了填充维数与上盒维数的关系.利用Cantor-Bendixson定理的方法,得到了由上盒维数给出的填充维数的等价定义.并证明了齐次Moran集对上盒维数和填充维数的连续性.     

Logistic混沌系统分形特性研究

对Logistic序列进行研究,利用Matlab数值模拟,通过计算不同初值、不同参数对应的混沌序列的计盒维数,得出结论:只要在数据充分的情况下,Logistic系统的分形维数基本由参数λ决定,与系统初值无关;同时计盒维数并非像熵一样随Logistic系统的参数λ增大而增大.     

Hausdorf Dimension of Quadratic Rational Julia Sets

Suppose a quadratic rational map has a Siegel disk and a parabolic fxed point.If the rotation number of the Siegel disk is an irrational of bounded type,then the Julia set of the map is shallow.This implies that its Hausdorf dimension is strictly less than two.     

Vector-valued fractal functions: Fractal dimension and fractional calculus

There are many research available on the study of a real-valued fractal interpolation function and fractal dimension of its graph. In this paper, our main focus is to study the dimensional results for a vector-valued fractal interpolation function and its Riemann–Liouville fractional integral. Here, we give some results which ensure that dimensional results for vector-valued functions are quite different from real-valued functions. We determine interesting bounds for the Hausdorff dimension of the graph of a vector-valued fractal interpolation function. We also obtain bounds for the Hausdorff dimension of the associated invariant measure supported on the graph of a vector-valued fractal interpolation function. Next, we discuss more efficient upper bound for the Hausdorff dimension of measure in terms of probability vector and contraction ratios. Furthermore, we determine some dimensional results for the graph of the Riemann–Liouville fractional integral of a vector-valued fractal interpolation function.     

盒维数的一个等价定义及其应用

给出了盒维数的一个等价定义．该定义与盒维数的现有定义相比,从理论上更容易验证,在应用中更适合于数值计算．据此给出了计算盒维数的一个数值算法．     

Sub-Riemannian vs. Euclidean dimension comparison and fractal geometry on Carnot groups

We solve Gromov's dimension comparison problem for Hausdorff and box counting dimension on Carnot groups equipped with a Carnot-Carathéodory metric and an adapted Euclidean metric. The proofs use sharp covering theorems relating optimal mutual coverings of Euclidean and Carnot-Carathéodory balls, and elements of sub-Riemannian fractal geometry associated to horizontal self-similar iterated function systems on Carnot groups. Inspired by Falconer's work on almost sure dimensions of Euclidean self-affine fractals we show that Carnot-Carathéodory self-similar fractals are almost surely horizontal. As a consequence we obtain explicit dimension formulae for invariant sets of Euclidean iterated function systems of polynomial type. Jet space Carnot groups provide a rich source of examples.     

Box dimension of Neimark–Sacker bifurcation

In this article we show how a change of a box dimension of orbits of two-dimensional discrete dynamical systems is connected to their bifurcations in a non-hyperbolic fixed point. This connection is already shown in the case of one-dimensional discrete dynamical systems and Hopf bifurcation for continuous systems. Namely, at the bifurcation point the box dimension changes from zero to a certain positive value which is connected to the appropriate bifurcation. We study a two-dimensional discrete dynamical system with only one multiplier on the unit circle, and show a result for the box dimension of an orbit on the centre manifold. We also consider a planar discrete system undergoing a Neimark–Sacker bifurcation. It is shown that box dimension depends on the order of non-degeneracy at the non-hyperbolic fixed point and on the angle–displacement map. As it was expected, we prove that the box dimension is different in the rational and irrational case.     

THE REGULARITY OF RANDOM GRAPH DIRECTED SELF-SIMILAR SETS

A set in R^d is called regular if its Hausdorff dimension coincides with its upper box counting dimension. It is proved that a random graph-directed self-similar set is regular a.e..     

Sur la dimension de boîte des graphes

We prove a formula which allows to deduce the box dimension of the graph of a function from its wavelet coefficients, and we give some consequences. We recall the main properties of lacunary wavelet series, and we calculate the box dimension of their graphs.     

松弛型并行多分裂方法解非线性方程组的安全界

本文对某些非线性方程组F(x)=0,导出了一个算法,用它可以迭代建立F(x)=0的解的紧致上、下界。算法基于某些矩阵的多分裂,因此具有自然的并行性。我们证明了趋向于解的界之收敛原则,给出了参数的收敛性区域并考察了方法的收敛速度。     

Limit cycle bifurcations of some Liénard systems

In this paper we first give some general theorems on the limit cycle bifurcation for near-Hamiltonian systems near a double homoclinic loop or a center as a preliminary. Then we use these theorems to study some polynomial Liénard systems with perturbations and give new lower bounds for the maximal number of limit cycles of these systems.     

Graph Compositions and Flats of Cycle Matroids

Abstract

We give an alternative method for counting the number of graph compositions of any graph G. In particular we show that counting the number of graph compositions of a graph G is equivalent to counting the number of flats of its cycle matroid. Then we give one condition for non isomorphic graphs to have the same number of graph compositions.     

Unstable directions and fractal dimension for skew products with overlaps in fibers

A unique feature of smooth hyperbolic non-invertible maps is that of having different unstable directions corresponding to different prehistories of the same point. In this paper we construct a new class of examples of non-invertible hyperbolic skew products with thick fibers for which we prove that there exist uncountably many points in the locally maximal invariant set ?? (actually a Cantor set in each fiber), having different unstable directions corresponding to different prehistories; also we estimate the angle between such unstable directions. We discuss then the Hausdorff dimension of the fibers of ?? for these maps by employing the thickness of Cantor sets, the inverse pressure, and also by use of continuous bounds for the preimage counting function. We prove that in certain examples, there are uncountably many points in ?? with two preimages belonging to ??, as well as uncountably many points having only one preimage in ??. In the end we give examples which, also from the point of view of Hausdorff dimension, are far from being homeomorphisms on ??, as well as far from being constant-to-1 maps on ??.     

Log-Convexity of Counting Processes Evaluated at a Random end of Observation Time with Applications to Queueing Models

We consider a counting processes with independent inter-arrival times evaluated at a random end of observation time T, independent of the process. For instance, this situation can arise in a queueing model when we evaluate the number of arrivals after a random period which can depend on the process of service times. Provided that T has log-convex density, we give conditions for the inter-arrival times in the counting process so that the observed number of arrivals inherits this property. For exponential inter-arrival times (pure-birth processes) we provide necessary and sufficient conditions. As an application, we give conditions such that the stationary number of customers waiting in a queue is a log-convex random variable. We also study bounds in the approximation of log-convex discrete random variables by a geometric distribution.