Complex systems (CS) are pervasive in many areas of science and technology, namely in financial markets, transportation, telecommunication and social networks, world and country economies, immunological systems, living organisms, computational systems, and electrical and mechanical structures. CS are often composed of a large number of interconnected and interacting entities, exhibiting a much richer global scale dynamics than their individual parts. This Special Issue focuses on original and new research results on CS and fractional dynamics. It comprises 12 selected manuscripts that address novel issues, as well as specific topics illustrating the broad impact of entropy and information theory-based techniques in complexity, nonlinearity, and fractionality. In the following, the manuscripts are presented in alphabetical order. In the paper "Analytical Approximate Solutions of (n + 1)-Dimensional Fractal Heat-Like and Wave-Like Equations", Omer Acan, Dumitru Baleanu, Maysaa Mohamed Al Qurashi, and Mehmet Giyas Sakar propose a new type of (n + 1)-dimensional reduced differential transform method (RDTM) based on a local fractional derivative (LFD) to solve (n + 1)-dimensional local fractional partial differential equations (PDEs) in Cantor sets. Firstly, the authors introduce the theoretical concepts. Afterwards, they apply the method to the (n + 1)-dimensional fractal heat-like equations (HLEs) and wave-like equations (WLEs). The authors conclude that the new technique is efficient and easy to apply [1] . The paper "A Novel Numerical Approach for a Nonlinear Fractional Dynamical Model of Interpersonal and Romantic Relationships", by Jagdev Singh, Devendra Kumar, Maysaa Al Qurashi, and Dumitru Baleanu, proposes the q-homotopy analysis Sumudu transform method (q-HASTM) to obtain the approximate solution for the nonlinear fractional dynamical model of interpersonal and romantic relationships. The results obtained by employing the proposed scheme reveal good accuracy, effectiveness, flexibility, and simplicity [2] . In the paper "Fractional Derivative Phenomenology of Percolative Phonon-Assisted Hopping in Two-Dimensional Disordered Systems", by Renat Sibatov, Vadim Shulezhko, and Vyacheslav Svetukhin, the anomalous advection-diffusion in two-dimensional semiconductor systems with coexisting energetic and structural disorder is described in the framework of a generalized model of multiple trapping on a comb-like structure. To validate the model, the authors compare the analytical solutions with the results of a Monte Carlo simulation of phonon-assisted tunneling in two-dimensional patterns of a porous nanoparticle agglomerate and a phase-separated bulk heterojunction. The variations of the anomalous advection-diffusion parameters as functions of the electric field intensity as well as levels of energetic and structural disorder are also presented [3] . In
While the software system can simulate, define, and control the business processes of the real world at a multilevel of granularity, the authors of REF introduced a series of research works based on original and new research results on complex systems (CS) and fractional dynamics, as well as specific topics illustrating the broad impact of entropy and information theory-based techniques.
Complex Systems and Fractional Dynamics
Entropy
Entropy
Mathematics Computer Science