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Gustavo Rodrigues Ferreira

Publications and source records attributed to Gustavo Rodrigues Ferreira.

8 recordsLinked to original sources
arXiv2026

Classifying multiply connected wandering domains

We study the internal dynamics of multiply connected wandering domains of meromorphic functions. We do so by considering the sequence of injectivity radii along the orbit of a base point, together with the hyperbolic distortions along the same orbit. The latter sequence has previously been used in this context; the former introduces geometric information about the shape of the wandering domains that interacts with the dynamical information given by the hyperbolic distortions. Using this idea, we complete the description of the internal dynamics of any wandering domain of a meromorphic function, and also unify previous approaches to the question. We conclude that the internal dynamics of a wandering domain, from the point of view of hyperbolic geometry, can be classified into six different types. Five of these types were previously known and are realised by wandering domains of entire functions. The sixth type arises only for meromorphic functions: a locally but not globally eventually isometric wandering domain. We construct a meromorphic function with such a domain, demonstrating that this new phenomenon does in fact occur. Our results show that, on a local level, the dynamical behaviour of wandering domains of meromorphic functions is similar to that which occurs of entire functions. However, new global phenomena can arise in the non-entire case. In particular, we identify a category of multiply connected wandering domains~-- essentially thin and infinitesimally non-contracting domains~-- that naturally generalise multiply connected wandering domains of entire functions, and share many characteristics with these. We generalise a number of results of Bergweiler, Rippon and Stallard for the entire case to this more general setting. In particular, we show the existence of dynamically meaningful singular foliations provided by level lines of certain positive harmonic functions.

math.DS↗
arXiv2023

Multiply connected wandering domains of meromorphic functions: the pursuit of uniform internal dynamics

Recently, Benini et al. showed that, in simply connected wandering domains of entire functions, all pairs of orbits behave in the same way relative to the hyperbolic metric, thus giving us our first insight into the general internal dynamics of such domains. After proving in a recent manuscript that the same is not true for multiply connected wandering domains, a natural question is: how inhomogeneous can multiply connected wandering domains be? We give an answer to this question, in that we show that uniform dynamics inside an open subset of the domain generalises to the whole wandering domain. As an application of this result, we construct the first example of a meromorphic function with a semi-contracting infinitely connected wandering domain.

math.DS↗
arXiv2022

A note on forward iteration of inner functions

A well-known problem in holomorphic dynamics is to obtain Denjoy--Wolff-type results for compositions of self-maps of the unit disc. Here, we tackle the particular case of inner functions: if $f_n:\mathbb{D}\to\mathbb{D}$ are inner functions fixing the origin, we show that a limit function of $f_n\circ\cdots\circ f_1$ is either constant or an inner function. For the special case of Blaschke products, we prove a similar result and show, furthermore, that imposing certain conditions on the speed of convergence guarantees $L^1$ convergence of the boundary extensions. We give a counterexample showing that, without these extra conditions, the boundary extensions may diverge at all points of $\partial\mathbb{D}$.

math.CV↗
arXiv2021

Multiply connected wandering domains of meromorphic functions: internal dynamics and connectivity

We discuss how the nine-way classification scheme devised by Benini et al. for the dynamics of simply connected wandering domains of entire functions, based on the long-term behaviour of the hyperbolic distance between iterates of pairs of points and also the distance between orbits and the domains' boundaries, carries over to the general case of multiply connected wandering domains of meromorphic functions. Most strikingly, we see that not all pairs of points in such a wandering domain behave in the same way relative to the hyperbolic distance, and that the connectivity of the wandering domain greatly influences its possible internal dynamics. After illustrating our results with the well-studied case of Baker wandering domains, we further illustrate the diversity of multiply connected wandering domains in general by constructing a meromorphic function with a wandering domain without eventual connectivity. Finally, we show that an analogue of the "convergence to the boundary" classification of Benini et al. does hold in general, and add new information about how this convergence takes place.

math.DS↗
arXiv2020

Escaping points of commuting meromorphic functions with finitely many poles

Let $f$ and $g$ be commuting meromorphic functions with finitely many poles. By studying the behaviour of Fatou components under this commuting relation, we prove that $f$ and $g$ have the same Julia set whenever $f$ and $g$ have no simply connected fast-escaping wandering domains. By combining this with a recent result of Tsantaris', we obtain the strongest statement (to date) regarding the Julia sets of commuting meromorphic functions. In order to highlight the difference to the entire case, we show that transcendental meromorphic functions with finitely many poles have orbits that alternate between approaching a pole and escaping to infinity at strikingly fast rates.

math.DS↗
arXiv2019

Symmetries for Julia sets of rational maps

Since the 1980s, much progress has been done in completely determining which functions share a Julia set. The polynomial case was completely solved in 1995, and it was shown that the symmetries of the Julia set play a central role in answering this question. The rational case remains open, but it was already shown to be much more complex than the polynomial one. Here, we offer partial extensions to Beardon's results on the symmetry group of Julia sets, and discuss them in the context of singularly perturbed maps.

math.DS↗
arXiv2018

Gene regulatory and signalling networks exhibit distinct topological distributions of motifs

The biological processes of cellular decision making and differentiation involve a plethora of signalling pathways and gene regulatory circuits. These networks, in their turn, exhibit a multitude of motifs playing crucial parts in regulating network activity. Here, we compare the topological placement of motifs in gene regulatory and signalling networks and find that it suggests different evolutionary strategies in motif distribution for distinct cellular subnetworks.

q-bio.MN↗