arXiv subjects

Jordi Canela

Publications and source records attributed to Jordi Canela.

16 recordsLinked to original sources

arXiv2026

Application of polynomial algebras to non-linear equation solvers

This paper presents a novel application of Jet Transport, a high-order automatic differentiation technique, to enhance classical numerical methods, with a focus on Newton's method. We prove a central theorem establishing that, under appropriate conditions, applying Jet Transport within a Newton iteration doubles the number of correct coefficients in the Taylor series approximation of the solution. This theoretical result is then extended to the practical case where the exact solution is unknown, demonstrating the expected quadratic convergence (error reduction from $ \varepsilon $ to $ \varepsilon^2 $) while simultaneously doubling the order of accuracy in the series expansion. The efficacy of the resulting Jet-Newton method is demonstrated through three illustrative examples: an academic problem validating the theoretical convergence rates, the solution of Kepler's equation, and a new continuation algorithm for computing zero-velocity curves in the circular restricted three-body problem. These examples showcase the method's capability to provide high-order semi-analytical approximations.

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arXiv2025

Boundedness and simple connectivity of the basins of attraction for some numerical methods

In this paper we study the dynamics of Halley's and Traub's root-finding algorithms applied to a symmetric family of polynomials of degree $d+1\geq 3$. We discuss the (un)boundedness and simple connectivity of the immediate basins of attraction of the fixed points associated to the roots of the polynomials. In particular, we show the existence of polynomials for which the immediate basin of attraction of a root is bounded under Halley's method

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arXiv2025

Connected McMullen-like Julia sets in a Chebyshev-Halley Family

In this paper we study a one parameter family of rational maps obtained by applying the Chebyshev-Halley root finding algorithms. We show that the dynamics near parameters where the family presents some degeneracy might be understood from the point of view of singular perturbations. More precisely, we relate the dynamics of those maps with the one of the McMullen family $M_λ(z)=z^4 + λ/z^2$, using quasi-conformal surgery.

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arXiv2025

On the basins of attraction of a one-dimensional family of root finding algorithms: from Newton to Traub

In this paper we study the dynamics of damped Traub's methods $T_δ$ when applied to polynomials. The family of damped Traub's methods consists of root finding algorithms which contain both Newton's ($δ=0$) and Traub's method ($δ=1$). Our goal is to obtain several topological properties of the basins of attraction of the roots of a polynomial $p$ under $T_1$, which are used to determine a (universal) set of initial conditions for which convergence to all roots of $p$ can be guaranteed. We also numerically explore the global properties of the dynamical plane for $T_δ$ to better understand the connection between Newton's method and Traub's method.

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arXiv2025

Dynamics of Newton-like root finding methods

When exploring the literature, it can be observed that the operator obtained when applying \textit{Newton-like} root finding algorithms to the quadratic polynomials $z^2-c$ has the same form regardless of which algorithm has been used. In this paper we justify why this expression is obtained. This is done by studying the symmetries of the operators obtained after applying Newton-like algorithms to a family of degree $d$ polynomials $p(z)=z^d-c$. Moreover, we provide an iterative procedure to obtain the expression of new Newton-like algoritms. We also carry out a dynamical study of the given generic operator and provide general conclusions of this type of methods.

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arXiv2025

Dynamics of a Family of Rational Operators of Arbitrary Degree

In this paper we analyse the dynamics of a family of rational operators coming from a fourth-order family of root-finding algorithms. We first show that it may be convenient to redefine the parameters to prevent redundancies and unboundedness of problematic parameters. After reparametrization, we observe that these rational maps belong to a more general family $O_{a,n,k}$ of degree $n+k$ operators, which includes several other families of maps obtained from other numerical methods. We study the dynamics of $O_{a,n,k}$ and discuss for which parameters $n$ and $k$ these operators would be suitable from the numerical point of view.

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arXiv2024

Computing parameter planes of iterative root-finding methods with several free critical points

In this paper we present an algorithm to obtain the parameter planes of families of root-finding methods with several free critical points. The parameter planes show the joint behaviour of all critical points. This algorithm avoids the inconsistencies arising from the relationship between the different critical points as well as the indeterminacy caused by the square roots involved in their computation. We analyse the suitability of this algorithm by drawing the parameter planes of different Newton-like methods with two and three critical points. We also present some results of the expressions of the Newton-like operators and their derivatives in terms of palindromic polynomials, and we show how to obtain the expression of the critical points of a Newton-like method with real coefficients.

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arXiv2021

Dynamical mechanism behind ghosts unveiled in a map complexification

Complex systems such as ecosystems, electronic circuits, lasers or chemical reactions can be modelled by dynamical systems which typically experience bifurcations. Transients typically suffer extremely long delays at the vicinity of bifurcations and it is also known that these transients follow scaling laws as the bifurcation parameter gets closer the bifurcation value in deterministic systems. The mechanisms involved in local bifurcations are well-known. However, for saddle-node bifurcations, the relevant dynamics after the bifurcation occur in the complex phase space. Hence, the mechanism responsible for the delays and the associated inverse-square root scaling law for this bifurcation can be better understood by looking at the dynamics in the complex space. We follow this approach and complexify a simple ecological system undergoing a saddle-node bifurcation. The discrete model describes a biological system with facilitation (cooperation) under habitat destruction for species with non-overlapping generations. We study the complex (as opposed to real) dynamics once the bifurcation has occurred. We identify the fundamental mechanism causing these long delays (called ghosts), given by two repellers in the complex space. Such repellers appear to be extremely close to the real line, thus forming a narrow channel close to the two new fixed points and responsible for the slow passage of the orbits, which remains tangible in the real numbers phase space. We analytically provide the relation between the inverse square-root scaling law and the multipliers of these repellers. We finally prove that the same phenomenon occurs for more general i.e., non-necessarily polynomial, models.

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arXiv2021

Achievable connectivities of Fatou components for a family of singular perturbations

In this paper we study the connectivity of Fatou components for maps in a large family of singular perturbations. We prove that, for some parameters inside the family, the dynamical planes for the corresponding maps present Fatou components of arbitrarily large connectivity and we determine precisely these connectivities. In particular, these results extend the ones obtained in [Can17, Can18].

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arXiv2019

Tips of Tongues in the Double Standard Family

We answer a question raised by Misiurewicz and Rodrigues concerning the family of degree 2 circle maps $F_λ:\mathbb{R}/\mathbb{Z}\to \mathbb{R}/\mathbb{Z}$ defined by \[F_λ(x) := 2x + a+ \frac{b}π \sin(2πx){\quad\text{with}\quad} λ:=(a,b)\in \mathbb{R}/\mathbb{Z}\times (0,1).\] We prove that if $F_λ^{\circ n}-{\rm id}$ has a zero of multiplicity $3$ in $\mathbb{R}/\mathbb{Z}$, then there is a system of local coordinates $(α,β):W\to \mathbb{R}^2$ defined in a neighborhood $W$ of $λ$, such that $α(λ) =β(λ)=0$ and $F_μ^{\circ n} - {\rm id}$ has a multiple zero with $μ\in W$ if and only if $β^3(μ) = α^2(μ)$. This shows that the tips of tongues are regular cusps.

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arXiv2018

Connectivity of the Julia set for the Chebyshev-Halley family on degree n polynomials

We study the Chebyshev-Halley family of root finding algorithms from the point of view of holomorphic dynamics. Numerical experiments show that the speed of convergence to the roots may be slower when the basins of attraction are not simply connected. In this paper we provide a criterion which guarantees the simple connectivity of the basins of attraction of the roots. We use the criterion for the Chebyshev-Halley methods applied to the degree $n$ polynomials $z^n+c$, obtaining a characterization of the parameters for which all Fatou components are simply connected and, therefore, the Julia set is connected. We also study how increasing $n$ affects the dynamics.

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arXiv2018

Julia sets with a wandering branching point

According to the Thurston No Wandering Triangle Theorem, a branching point in a locally connected quadratic Julia set is either preperiodic or precritical. Blokh and Oversteegen proved that this theorem does not hold for higher degree Julia sets: there exist cubic polynomials whose Julia set is a locally connected dendrite with a branching point which is neither preperiodic nor precritical. In this article, we reprove this result, constructing such cubic polynomials as limits of cubic polynomials for which one critical point eventually maps to the other critical point which eventually maps to a repelling fixed point.

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arXiv2017

Rational maps with Fatou components of arbitrarily large connectivity

We study the family of singular perturbations of Blaschke products $B_{a,λ}(z)=z^3\frac{z-a}{1-\overline{a}z}+\fracλ{z^2}$. We analyse how the connectivity of the Fatou components varies as we move continuously the parameter $λ$. We prove that all possible escaping configurations of the critical point $c_-(a,λ)$ take place within the parameter space. In particular, we prove that there are maps $B_{a,λ}$ which have Fatou components of arbitrarily large finite connectivity within their dynamical planes.

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arXiv2017

Singular perturbations of Blaschke Products and connectivity of Fatou components

The goal of this paper is to study the family of singular perturbations of Blaschke products given by $B_{a,λ}(z)=z^3\frac{z-a}{1-\overline{a}z}+\fracλ{z^2}$. We focus on the study of these rational maps for parameters $a$ in the punctured disk $\mathbb{D}^*$ and $|λ|$ small. We prove that, under certain conditions, all Fatou components of a singularly perturbed Blaschke product $B_{a,λ}$ have finite connectivity but there are components of arbitrarily large connectivity within its dynamical plane. Under the same conditions we prove that the Julia set is the union of countably many Cantor sets of quasicircles and uncountably many point components.

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arXiv2015

Tongues in Degree 4 Blaschke Products

The goal of this paper is to investigate the family of Blasche products $B_a(z)=z^3\frac{z-a}{1-\bar{a}z}$, which is a rational family of perturbations of the doubling map. We focus on the tongue-like sets which appear in its parameter plane. We first study their basic topological properties and afterwords we investigate how bifurcations take place in a neighborhood of their tips. Finally we see how the period one tongue extends beyond its natural domain of definition.

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arXiv2015

On a Family of Rational Perturbations of the Doubling Map

The goal of this paper is to investigate the parameter plane of a rational family of perturbations of the doubling map given by the Blaschke products $B_a(z)=z^3\frac{z-a}{1-\bar{a}z}$. First we study the basic properties of these maps such as the connectivity of the Julia set as a function of the parameter $a$. We use techniques of quasiconformal surgery to explore the relation between certain members of the family and the degree 4 polynomials $\left(\overline{\overline{z}^2+c}\right)^2+c$. In parameter space, we classify the different hyperbolic components according to the critical orbits and we show how to parametrize those of disjoint type.

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