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1984, Transactions of the American Mathematical Society
By a theorem of S. Demko there exists a balanced measure on the Julia set of an arbitrary nonlinear rational transformation on the Riemann sphere. It is proved here that if the transformation admits an attractive or indifferent cycle, then there is a point with respect to which all the moments of a balanced measure exist; moreover, these moments can be calculated exactly. An explicit balanced measure is exhibited in an example where the Julia set is the whole sphere and for which the moments, with respect to any point, do not all exist.
Bulletin of the American Mathematical Society, 1982
Arxiv preprint math/9402215, 1994
In this paper we shall show that there exists ℓ 0 such that for each even integer ℓ ≥ ℓ 0 there exists c 1 ∈ R for which the Julia set of z → z ℓ + c 1 has positive Lebesgue measure. This solves an old problem. Editor's note: In 1997, it was shown by Xavier Buff that there was a serious flaw leaving a gap in the proof. Currently (1999), the question of positive measure Julia sets remains open. * A mistake which was pointed out to us by J.C. Yoccoz has been corrected in this version † e-mail: strien at fwi.uva.nl. ‡ supported by the NWO, KBN-GR91. S. van Strien and T. Nowicki 6 Quasiconformal rigidity of the return maps; renormalization and the proof of Theorem A 25 7 The random walk argument 42 8 A nested sequence of discs 43 9 An induced mapping with Markov properties 58 10 An asymptotic expression for the real induced map 64 10.
Proceedings of the American Mathematical Society, 2008
If the preimage of a four-point set under a meromorphic function belongs to the real line, then the image of the real line is contained in a circle in the Riemann sphere. We include an application of this result to holomorphic dynamics: if the Julia set of a rational function is contained in a smooth curve, then it is contained in a circle.
1995
Let $f:\bar\bold C\to\bar\bold C$ be a rational map on the Riemann sphere , such that for every $f$-critical point $c\in J$ which forward trajectory does not contain any other critical point, $|(f^n)'(f(c))|$ grows exponentially fast (Collet--Eckmann condition), there are no parabolic periodic points, and else such that Julia set is not the whole sphere. Then smooth (Riemann) measure of the
arXiv: Complex Variables, 2018
Let $f$ be a transcendental entire function with at least one critical point and let $\alpha$ be an entire function such that (i) $T(r,\alpha)=S(r,f)$ as $r\to\infty ,$ (ii) $\alpha$ has at least one zero, (iii) $\alpha ^{\prime}$ has no common zeros with $f^{\prime}.$ In this paper we show that if $g$ is any transcendental entire function permutable with $f_a(z) := f(z) + a\alpha (z),$ then $g$ and $f_a$ have identical Julia sets as long as $a$ is outside some denumerable subset of $\mathbb{C}$; this answers Baker's question for almost all nonlinear entire functions.
We extend results by Barnsley et al. about orthogonal polynomials on Julia sets to the case of generalized Julia sets. The equilibrium measure is considered. In addition, we discuss optimal smoothness of Green's functions and Widom criterion for a special family of real generalized Julia sets.
Mathematical Proceedings of the Cambridge Philosophical Society, 2008
The asymptotic behaviour of the solutions of Poincaré's functional equation f(λz) = p(f(z)) (λ > 1) for p a real polynomial of degree ≥ 2 is studied in angular regions W of the complex plain. It is known [9, 10] that f(z) ~ exp(zρF(logλz)), if f(z) → ∞ for z ∞ and z ∈ W, where F denotes a periodic function of period 1 and ρ = logλ deg(p). In this paper we refine this result and derive a full asymptotic expansion. The constancy of the periodic function F is characterised in terms of geometric properties of the Julia set of p. For real Julia sets we give inequalities for multipliers of Pommerenke-Levin-Yoccoz type. The distribution of zeros of f is related to the harmonic measure on the Julia set of p.
Topology and its Applications, 2018
In memory of Sibe Mardešić, our friend. Sibe Mardešić has enriched algebraic topology developing shape and strong shape theories with important constructions and theorems. This paper relates computational topology to shape theory. We have developed some algorithms and implementations that under some conditions give a shape resolution of some Julia sets. When a semi-flow is induced by a rational map g of degree d defined on the Riemann sphere, one has the associated Julia set J(g). The main objective of this paper is to give a computational procedure to study the shape of the compact metric space J(g). Our main contribution is to provide an inverse system of cubic complexes approaching J(g) by using implemented algorithms based in the notion of spherical multiplier. This inverse system of cubical complexes is used to: (i) obtain nice global visualizations of the fractal structure of the Julia set J(g); (ii) determine the shape of the compact metric space J(g). These techniques also give the possibility of applying overlay theory (introduced by R. Fox and developed among others by S. Mardešić) to study the symmetry properties of the fractal geometry of the Julia set J(g).
Qualitative Theory of Dynamical Systems, 2004
In this paper we consider families of rational maps of degree 2n on the Riemann sphere F λ : C → C given by F λ (z) = z n + λ z n where λ ∈ C − {0} and n ≥ 2. One of our goals in this paper is to describe a type of structure that we call a Cantor necklace that occurs in both the dynamical and the parameter plance for F λ. Roughly speaking, such a set is homeomorphic to a set constructed as follows. Start with the Cantor middle thirds set embedded on the x-axis in the plane. Then replace each removed open interval with an open circular disk whose diameter is the same as the length of the removed interval. A Cantor necklace is a set that is homeomorphic to the resulting union of the Cantor set and the adjoined open disks. The second goal of this paper is to use the Cantor necklaces in the parameter plane to prove the existence of several new types of Sierpinski curve Julia sets that arise in these families of rational maps. Unlike most examples of this type of Julia set, the maps on these Julia sets are structurally unstable. That is, small changes in the parameter λ give rise to Julia sets on which the dynamical behavior is quite different. In addition, we also describe a new type of related Julia set which we call a hybrid Sierpinski curve.
Inventiones mathematicae, 2017
We construct a non-polynomial entire function whose Julia set has finite 1-dimensional spherical measure, and hence Hausdorff dimension 1. In 1975, Baker proved the dimension of such a Julia set must be at least 1, but whether this minimum could be attained has remained open until now. Our example also has packing dimension 1, and is the first transcendental Julia set known to have packing dimension strictly less than 2. It is also the first example with a multiply connected wandering domain where the dynamics can be completely described.
Let f k g 1 k=1 be a sequence of not necessarily distinct points on the complex unit circle. We consider the moment problem where it is to nd a positive measure on
Acta Mathematica Hungarica, 1996
Mathematical Proceedings of the Cambridge …, 2005
We study the dynamics of non-entire transcendental meromorphic functions with a finite asymptotic value mapped after some iterations onto a pole. This situation does not appear in the case of rational or entire functions. We consider the family of non-entire functions
This paper presents a criterion for a Julia set of a rational map of the form F λ (z) = z 2 + λ/z 2 to be a Sierpinski curve.
Annals of Mathematics, 2012
We prove the existence of quadratic polynomials having a Julia set with positive Lebesgue measure. We find such examples with a Cremer fixed point, with a Siegel disk, or with infinitely many satellite renormalizations. Contents © in the halfplane ¶ z ∈ C ; |z| > |z − σ n | ©. This takes care of τ n (P n ∩ H −). The map τ n is a universal covering from the upper half-plane H + := ¶ w ∈ C ; Im(w) > 0 © to the punctured half-plane ¶ z ∈ C ; 0 < |z| < |z − σ n | © , with covering transformation group generated by the translation T n : w → w + 1/α n. It sends the lines L k := ß w ∈ C ; Re(w) = 2k + 1 2α n ™ , k ∈ Z to the segment ]0, σ n [. It is therefore enough to show that there is a constant M such that for n large enough, P n ∩ H + is contained in the vertical strip ß w ∈ C ; − M α n < Re(w) < M α n ™ .
Computers & Graphics, 1993
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2006
We consider the harmonic measure on a disconnected polynomial Julia set in terms of Brownian motion. We show that the harmonic measure of any connected component of such a Julia set is zero. Associated to the polynomial is a combinatorial model, the tree with dynamics. We define a measure on the tree, which is a combinatorial version on harmonic measure. We show that this measure is isomorphic to the harmonic measure on the Julia set. The measure induces a random walk on the tree, which is isomorphic to Brownian motion in the plane.
Journal of Statistical Physics, 1984
For real 2 a correspondence is made between the Julia set B a for z-* (z-2) 2, in the hyperbolic case, and the set of 2-chains {2 • ~-A • ,v/(A + ... }, with the aid of Cremer's theorem. It is shown how a number of features of B a can be understood in terms of A-chains. The structure of B a is determined by certain equivalence classes of 2-chains, fixed by orders of visitation of certain real cycles; and the bifurcation history of a given cycle can be conveniently computed via the combinatorics of 2-chains. The functional equations obeyed by attractive cycles are investigated, and their relation to 2-chains is given. The first cascade of period-doubling bifurcations is described from the point of view of the associated Julia sets and 2-chains. Certain "Julia sets" associated with the Feigenbaum function and some theorems of Lanford are discussed.
Mathematische Annalen, 2010
Let f be a transcendental entire function for which the set of critical and asymptotic values is bounded. The Denjoy-Carleman-Ahlfors theorem implies that if the set of all z for which |f (z)| > R has N components for some R > 0, then the order of f is at least N/2. More precisely, we have log log M (r, f) ≥ 1 2 N log r − O(1), where M (r, f) denotes the maximum modulus of f. We show that if f does not grow much faster than this, then the escaping set and the Julia set of f have positive Lebesgue measure. However, as soon as the order of f exceeds N/2, this need not be true. The proof requires a sharpened form of an estimate of Tsuji related to the Denjoy-Carleman-Ahlfors theorem.
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