Complex dynamics in two-dimensional coupling of quadratic maps

Anca Rădulescu, Eva Kaslik, Alexandru Fikl

Chaos, Solutions & Fractals

Abstract

In our previous work, we initiated the study of dynamics in networks with identical nodes that evolve under complex quadratic iterations. For these Complex Quadratic Networks, (or CQNs for short), we focused on defining the equi-M set as the natural extension of the Mandelbrot set, representing the locus of complex parameters for which the network's critical orbit remains bounded. This paper examines the structure and limitations of equi-M sets in two-dimensional Complex Quadratic Networks (CQNs). In particular, we aim to describe the relationship between the equi-M set and the parameter domains where the critical orbit converges to periodic attractors. The simplest case of two coupled nodes serves as a foundational testbed: its analytical tractability enables the identification of critical phenomena and their dependence on coupling, while offering insight into more general principles. The two-node case is also simple enough to allow for explicit characterization of the coupling conditions that govern transitions between synchronized and desynchronized behavior. Using a combination of analytical and numerical methods, the study reveals that while the parameter region corresponding to an attracting fixed point closely tracks the boundary of the equi-M set near its main cusp, this correspondence breaks down for higher periods and in regions supporting coexisting attractors. These discrepancies highlight key differences between uncoupled one-dimensional dynamics and coupled systems, where equi-M sets capture only partial information about the system's global combinatorics. Overall, the results illustrate how coupling transforms the familiar structure of the Mandelbrot set into a richer, higher-dimensional landscape for low-dimensional CQNs and point toward a sharp increase in complexity as the number of nodes grows. This work bridges classical complex dynamics with emerging questions in networked nonlinear systems and lays the groundwork for analyzing high-dimensional coupled dynamics.

BibTeX

@article{RadulescuKaslikFikl2026,
  title         = {Asymptotic Dynamics in Systems of Two Coupled Quadratic Maps},
  author        = {Anca R\u{a}dulescu and Eva Kaslik and Alexandru Fikl},
  year          = 2026,
  month         = jan,
  journal       = {Chaos, Solitons \& Fractals},
  publisher     = {Elsevier {BV}},
  volume        = 202,
  pages         = {117489--117489},
  doi           = {10.1016/j.chaos.2025.117489},
  abstract      = {
    In our previous work, we initiated the study of dynamics in networks with
    identical nodes that evolve under complex quadratic iterations. For these
    Complex Quadratic Networks, (or CQNs for short), we focused on defining the
    equi-M set as the natural extension of the Mandelbrot set, representing the
    locus of complex parameters for which the network's critical orbit remains
    bounded.

    This paper examines the structure and limitations of equi-M sets in
    two-dimensional Complex Quadratic Networks (CQNs). In particular, we aim to
    describe the relationship between the equi-M set and the parameter domains
    where the critical orbit converges to periodic attractors. The simplest
    case of two coupled nodes serves as a foundational testbed: its analytical
    tractability enables the identification of critical phenomena and their
    dependence on coupling, while offering insight into more general
    principles. The two-node case is also simple enough to allow for explicit
    characterization of the coupling conditions that govern transitions between
    synchronized and desynchronized behavior.

    Using a combination of analytical and numerical methods, the study reveals
    that while the parameter region corresponding to an attracting fixed point
    closely tracks the boundary of the equi-M set near its main cusp, this
    correspondence breaks down for higher periods and in regions supporting
    coexisting attractors. These discrepancies highlight key differences
    between uncoupled one-dimensional dynamics and coupled systems, where
    equi-M sets capture only partial information about the system's global
    combinatorics. Overall, the results illustrate how coupling transforms the
    familiar structure of the Mandelbrot set into a richer, higher-dimensional
    landscape for low-dimensional CQNs and point toward a sharp increase in
    complexity as the number of nodes grows. This work bridges classical
    complex dynamics with emerging questions in networked nonlinear systems and
    lays the groundwork for analyzing high-dimensional coupled dynamics.
  },
}