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Complexities

Complexities is an international, peer-reviewed, open access journal on complex systems, published quarterly online by MDPI.

All Articles (7)

Hypergraphs, a generalisation of traditional graphs in which hyperedges may connect more than two vertices, provide a natural framework for modeling higher-order interactions in complex biological systems. In the context of protein complexes, hypergraphs capture relationships in which a single protein may participate in multiple complexes simultaneously. A fundamental question is how such protein complex hypergraphs evolve over time. Motivated by duplication–divergence–deletion models often used for protein–protein interaction networks, we propose a novel Duplication–Divergence Hypergraph (DDH) model for the evolutionary dynamics of protein complex hypergraphs. To evaluate network resilience, we simulate targeted attack strategies analogous to drug treatments or genetic knockouts that remove selected proteins and their associated hyperedges. We measure the resulting structural changes using hypergraph-based efficiency metrics, comparing synthetic networks generated by the DDH model with empirical E. coli protein complex data. This framework demonstrates closer alignment with empirical observations than standard pairwise duplication–divergence models, suggesting that hypergraphs provide a more realistic representation of protein interactions.

3 December 2025

Scaled DDH hyperedge process starting from hyperedges of different sizes, with 
  
    p
    =
    0.55
  
 and maximum hyperedge size 3. The scaling exponent 
  α
 is set to be 
  
    3
    (
    1
    −
    p
    )
    =
    1.35
  
. The simulated behaviour is consistent with Theorem 2: within 5000 steps, the red trajectory (
  
    λ
    <
    α
  
) diverges, the blue trajectory (
  
    λ
    >
    α
  
) decays to zero, and only the green trajectory (
  
    λ
    =
    α
  
) stabilises at a non-trivial limit.

The Concept of Homeodynamics in Systems Theory

  • Hugues Petitjean,
  • Serge Finck and
  • Patrick Schmoll
  • + 1 author

This review traces the historical evolution, conceptual foundations, and contemporary applications of the term homeodynamics across biological, ecological, cognitive, and social systems. Initially coined in the 19th century but largely forgotten, the term re-emerged in the second half of the 20th century as scholars sought to describe dynamic stability in open, self-organizing systems. From Yates’s theoretical formalization in biology to Rattan’s work in biogerontology and recent applications in psychology and organizational theory, homeodynamics has progressively evolved from a synonym of homeostasis to a distinct systems concept. It now denotes the capacity of complex systems to sustain coherence through transitions between multiple temporary equilibria, integrating feedbacks, bifurcations, and adaptive reconfigurations. By revisiting the term’s lineage, this review clarifies its epistemological scope and proposes its use as a heuristic and modeling framework for understanding dynamic stability and regime shifts in living and social systems.

27 November 2025

Evolution of the term homeodynamics over time. The x-axis represents calendar years, from 1940 to 2025. The left y-axis is the number of articles containing the term homeodynamic (noun) from Google Scholar (black bars) and the right y-axis is from PubMed (gray bars).

Forecasting Chaotic Dynamics Using a Hybrid System

  • Michele Baia,
  • Franco Bagnoli and
  • Tommaso Matteuzzi

The literature is rich with studies and examples on parameter estimation obtained by analyzing the evolution of chaotic dynamical systems, even when only partial information is available through observations. However, parameter estimation alone does not resolve prediction challenges, particularly when only a subset of variables is known or when parameters are estimated with a significant uncertainty. In this paper, we introduce a hybrid system specifically designed to address this issue. Our method involves training an artificial intelligence system to predict the dynamics of a measured system by combining a neural network with a simulated system. By training the neural network, it becomes possible to refine the model’s predictions so that the simulated dynamics synchronizes with that of the system under investigation. After a brief contextualization of the problem, we introduce the hybrid approach employed, describing the learning technique and testing the results on three chaotic systems inspired by atmospheric dynamics in measurement contexts. Although these systems are low-dimensional, they encompass all the fundamental characteristics and predictability challenges that can be observed in more complex real-world systems.

20 November 2025

Schematic representation of the prediction process. The system is trained to predict the trajectory over a time window 
  
    t
    P
  
 based on a set of measurements. Assimilation occurs during a time window 
  
    t
    A
  
, in which the system state is reinitialized with the available measurements (red markers in the figure). The figure also shows the network’s predictions at the measurement times (blue dots).

Extended Gauss Iterative Map: Bistability and Chimera States

  • Derik W. Gryczak,
  • Ervin K. Lenzi and
  • Antonio M. Batista

We investigate an extended Gauss iterative map by incorporating the q-exponential function, a key component of the Tsallis framework. This extension enables us to investigate the non-linear dynamics of the Gauss iterative map across a broader range of scenarios, encompassing periodic, chaotic, and bistable behaviors. Regular and chaotic phenomena have been observed in coupled systems. In this context, we propose a network of coupled extended Gauss iterative maps. In our network, we found the emergence of chimera states, characterized by the coexistence of coherent and incoherent behaviors. These states are identified within specific parameter regimes using Gopal’s metric. In this work, we show the interplay between chaos and emergent collective dynamics in coupled extended Gauss iterative maps.

13 November 2025

This figure shows the behavior of the q-Gaussian for different values of q.

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Complexities - ISSN 3042-6448