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We study the group TA of rearrangements of the airplane limit space introduced by Belk and Forrest (2019). We prove that TA is generated by a copy of Thompson's group F and a copy of Thompson's group T, hence it is finitely generated. Then we study the commutator subgroup [TA; TA], proving that the abelianization of TA is isomorphic to Z and that [TA; TA] is simple, finitely generated and acts 2-transitively on the so-called components of the airplane limit space. Moreover, we show that TA is contained in T and contains a natural copy of the basilica rearrangement group TB studied by Belk and Forrest (2015). [ABSTRACT FROM AUTHOR]

This paper proposes a criterion for fractionalizing traditional fractal sets, and reports several fractional generalizations of the Julia set and Mandelbrot set of the classic quadratic map. The discrepancies among those extensions are investigated preliminarily. The influence of the map's memory effect on its fractal sets is discussed through visualization techniques and dimension analysis. [ABSTRACT FROM AUTHOR]

Julia set is one of the most important branches in fractal theory, and has achieved much progress on both theoretical analysis and application research. Nevertheless, most of the existing investigations relied on the systems with known parameters. Few works have been done on the inverse problem about how to determine the system parameter based on a given Julia set's shape. This work aims to address this issue by starting with the most classical polynomial map. First, by constructing a proper fitness function measuring the Julia sets' area error, the Julia sets' parameter estimation is formulated as a kind of optimization problem. According to the known conditions of Julia set to be estimated, the optimization problem is classified into two cases. For one case, when both the shape and size of Julia set are given, we only need to estimate the system's own parameter c. For the other case, when the Julia set has only a shape, we redesign the problem into three dimensions by adding a new scaling factor parameter γ and applying the partial coverage principle. Second, a particle swarm optimization (PSO) approach including dynamically adjustment strategy is adopted to solve the proposed optimization problem. At last, we present seven groups of simulations in which both randomly generated Julia sets and those in existing literature (or on the internet) are included. The simulation results verify the effectiveness of the proposed parameter estimation scheme. [ABSTRACT FROM AUTHOR]

In 2021, Mork and Ulness studied the Mandelbrot and Julia sets for a generalization of the well-explored function hl(z) = z2 +l. Their generalization was based on the composition of hl with the Möbius transformation m(z) = 1z at each iteration step. Furthermore, they posed a conjecture providing a relation between the coefficients of (each order) iterated series of m(hl(z)) (at z = 0) and the Catalan numbers. In this paper, in particular, we prove this conjecture in a more precise (quantitative) formulation. [ABSTRACT FROM AUTHOR]

This work reports on a study of the Mandelbrot set and Julia set for a generalization of the well-explored function h(z) = z2 + l. The generalization consists of composing with a fixed Möbius transformation at each iteration step. In particular, affine and inverse Möbius transformations are explored. This work offers a new way of visualizing the Mandelbrot and filled-in Julia sets. An interesting and unexpected appearance of hyperbolic triangles occurs in the structure of the Mandelbrot sets for the case of inverse Möbius transforms. Several lemmas and theorems associated with these types of fractal sets are presented. [ABSTRACT FROM AUTHOR]

In this paper, a Julia multiband fractal is designed for use in wireless communication applications. The proposed antenna contains Julia set embedded on FR epoxy substrate with thickness 1mm. Perturbations in the Julia fractal is also studied. The antenna has different characteristics and values because of perturbations. [ABSTRACT FROM AUTHOR]

We consider a solution to the problem of copyright protection by embedding a secret message into a still color or grayscale image using algebraic fractals. The peculiarity of the proposed steganographic method is the use of a two-dimensional fractal image of algebraic type as an intermediate cover image. For this purpose, it is proposed to use a fractal image of algebraic type in the form of a Julia set as an intermediate cover image. An attacker will not be able to generate an identical fractal image without the exact value of some complex number , which is agreed in advance between the sender and the recipient, as well as a number of other parameters, which makes the proposed method resistant to attacks. The advantage of the proposed algorithm is the ability to extract the watermark without knowledge of the original cover image, since the intermediate container for the watermark is a fractal. In this paper we consider fractal image generation techniques. Then generated fractals are used as cover image in steganography system. Watermark embeds in blue component of JPEG image. To assess the quality of obtained results, a quality assessment was made based on the following metrics: normalized mean square error (NMSE) and peak signal-to-noise ratio (PSNR), expressed in decibels. The results of the original cover image and stego image, as well as the original and extracted watermark, are presented. Analysis of the results of the evaluation of the quality of the original cover image and watermarked image, as well as the original and extracted watermark showed that the proposed algorithm provides high quality of hiding confidential information. The use of fractals as an intermediate cover image for the extraction of watermark allows ensuring the extraction practically without losses, while the stego image visually does not differ from the container containing classified information.

The work belongs to the direction of experimental mathematics, which investigates the properties of mathematical objects by the computing facilities of a computer. The base is an exponential map, its topological properties (Cantor's bouquets) differ from properties of polynomial and rational complex-valued functions. The subject of the study are the character and features of the Fatou and Julia sets, as well as the equilibrium points and orbits of the zero of three iterated complex-valued mappings: $f:z \to (1+ \mu) \exp (iz)$, $g : z \to \big(1+ \mu |z - z^*|\big) \exp (iz)$, $h : z \to \big(1+ \mu (z - z^* )\big) \exp (iz)$, with $z,\mu \in \mathbb{C}$, $z^* : \exp (iz^*) = z^*$. For a quasilinear map g having no analyticity characteristic, two bifurcation transitions were discovered: the creation of a new equilibrium point (for which the critical value of the linear parameter was found and the bifurcation consists of "fork" type and "saddle"-node transition) and the transition to the radical transformation of the Fatou set. A nontrivial character of convergence to a fixed point is revealed, which is associated with the appearance of "valleys" on the graph of convergence rates. For two other maps, the monoperiodicity of regimes is significant, the phenomenon of "period doubling" is noted (in one case along the path $39\to 3$, in the other along the path $17\to 2$), and the coincidence of the period multiplicity and the number of sleeves of the Julia spiral in a neighborhood of a fixed point is found. A rich illustrative material, numerical results of experiments and summary tables reflecting the parametric dependence of maps are given. Some questions are formulated in the paper for further research using traditional mathematics methods.

In 2021, Mork and Ulness studied the Mandelbrot and Julia sets for a generalization of the well-explored function ηλ(z)=z2+λ. Their generalization was based on the composition of ηλ with the Möbius transformation μ(z)=1z at each iteration step. Furthermore, they posed a conjecture providing a relation between the coefficients of (each order) iterated series of μ(ηλ(z)) (at z=0) and the Catalan numbers. In this paper, in particular, we prove this conjecture in a more precise (quantitative) formulation.

This work reports on a study of the Mandelbrot set and Julia set for a generalization of the well-explored function η(z)=z2+λ. The generalization consists of composing with a fixed Möbius transformation at each iteration step. In particular, affine and inverse Möbius transformations are explored. This work offers a new way of visualizing the Mandelbrot and filled-in Julia sets. An interesting and unexpected appearance of hyperbolic triangles occurs in the structure of the Mandelbrot sets for the case of inverse Möbius transforms. Several lemmas and theorems associated with these types of fractal sets are presented.

This paper presents an improvement of the sixth-order method of Chun and Neta as a class of three-step iterations with optimal efficiency index, in the sense of Kung-Traub conjecture. Each member of the presented class reaches the highest possible order using four functional evaluations. Error analysis will be studied and numerical examples are also made to support the theoretical results. We then present results which describe the dynamics of the presented optimal methods for complex polynomials. The basins of attraction of the existing optimal methods and our methods are presented and compared to illustrate their performances. [ABSTRACT FROM AUTHOR]

Escape time algorithm is a classical algorithm to calculate the Julia sets, but it has the disadvantage of dull color and cannot record the iterative process of the points. In this paper, we present the equipotential point algorithm to calculate the Julia sets by recording the strike frequency of the points in the iterative process. We calculate and analyze the Julia sets in the complex plane by using this algorithm. Finally, we discuss the iteration trajectory of a single point. [ABSTRACT FROM AUTHOR]

Given a complex polynomial p( z) with at least three distinct roots, we first prove that no rational iteration function exists where the basin of attraction of a root coincides with its Voronoi cell. In spite of this negative result, we prove that the Voronoi diagram of the roots can be well approximated through a high order sequence of iteration functions, the Basic Family, B( z), m≥2. Let θ be a simple root of p( z), V( θ) its Voronoi cell, and A( θ) its basin of attraction with respect to B( z). We prove that given any closed subset C of V( θ), including any homothetic copy of V( θ), there exists m such that for all m≥ m, C is also a subset of A( θ). This implies that when all roots of p( z) are simple, the basins of attraction of B( z) uniformly approximate the Voronoi diagram of the roots to within any prescribed tolerance. Equivalently, the Julia set of B( z), and hence the chaotic behavior of its iterations, will uniformly lie to within prescribed strip neighborhood of the boundary of the Voronoi diagram. In a sense, this is the strongest property a rational iteration function can exhibit for polynomials. Next, we use the results to define and prove an infinite layering within each Voronoi cell of a given set of points, whether known implicitly as roots of a polynomial equation, or explicitly via their coordinates. We discuss potential application of our layering in computational geometry. [ABSTRACT FROM AUTHOR]

In order to further enrich the form of 3D Mandelbrot and Julia sets, this paper first presents two methods of generating 3D fractal sets by utilizing discrete modifications of the standard quaternion algebra and analyzes the limitations in them. To overcome these limitations, a novel method for generating 3D fractal sets based on a 3D number system named ternary algebra is proposed. Both theoretical analyses and experimental results demonstrate that the ternary-algebra-based method is superior to any one of the quad-algebra-based methods, including the first two methods presented in this paper, because it is more intuitive, less time consuming and can completely control the geometric structure of the resulting sets. A ray-casting algorithm based on period checking is developed with the goal of obtaining high-quality fractal images and is used to render all the fractal sets generated in our experiments. It is hoped that the investigations conducted in this paper would result in new perspectives for the generalization of 3D Mandelbrot and Julia sets and for the generation of other deterministic 3D fractals as well. [ABSTRACT FROM AUTHOR]

Independence polynomials of graphs enjoy the property of essentially being closed under graph composition (or ‘lexicographic product’). We ask here: for higher products of a graph G with itself, where are the roots of their independence polynomials approaching? We prove that in fact they converge (in the Hausdorff topology) to the Julia set of the independence polynomial of G, thereby associating with G a fractal. The question arises as to when these fractals are connected, and for graphs with independence number 2 we exploit the Mandelbro¨t set to answer the question completely. [Copyright &y& Elsevier]

Newton''s transformation fw(z)=z−1/(wzw−1) containing only one complex parameter w (w≠0 or 1) is constructed from the transcendental mapping F(z)=ezw+c. Although the number of critical points of fw(z) is countably infinite, a method based on the Valid Critical Point Set, vcps={zk∈C−π, is discussed for the generation of the generalized Mandelbrot set M of fw(z). The petal fragments, the multi-period fragments, and the classical “Mandelbrot set” fragments are found in M. The dynamical characteristics of fw(z) for different values of w are analyzed. The relationship between the parameter w in a classical “Mandelbrot set” fragment and the structure of the corresponding filled-in Julia set is investigated. A large number of novel images of filled-in Julia sets are generated based on the rate of convergence of orbits. [Copyright &y& Elsevier]

To improve the efficiency to find the Julia point in Newton chaos iteration methods, by constructing repulsion three-cycle point function and making use of inverse-image iterative methods, a new method to find Julia set point was introduced. A new method to find all solutions based on utilizing sensitive fraetal areas to locate the Julia set point to find all solutions of the nonlinear questions was proposed. The developed technique uses an important feature of fractals to preserve the shape of basins of attraction on infinitely small scales. The numerical examples in planar crank-slide mechanisms show that the method is effective. [ABSTRACT FROM AUTHOR]