Complex Systems and Dynamics Group

Members

  • Dr. Bao-Ngoc Tran: Quasi-steady-state approximation, Fractional calculus, Inverse problems
  • Nesibe Ayhan, M.Sc.: Nonlinear dispersive equations, Attractors
  • Fabian Veider, M.Sc.: Opinion dynamics, Networked models
  • Juan Yang, M.Sc.: Reaction-diffusion systems, Attractors


    • Visiting members

  • Assoc. Dr. Duc-Thuan Do (8/2023 - 9/2023): Control and Optimisation, Stabilisation
  • Dr. Cordula Reisch (9/2023 - 12/2023): Modelling, Pattern formation
  • Dr. Lien Nguyen (03/2024 - 08/2024): Boundary equilibria, PDE, Plurisubhamornic functions
  • Qasim Khan, M.Sc. (11/2023 - 07/2024): Numerical methods
  • Thi-Hue Vu, M.Sc. (9/2023): Stochastic differential equations


    • Seminars

    Applied Analysis, Complex Systems & Dynamics

    Together with the Applied Analyis and Applied Mathematics groups, we are organising a weakly seminar on Tuesday, which is also streamed online. More details can be seen at the seminar website.

    Group seminars

  • Thursday 28.03.2024, SR 11.34

    • 10:00 - 11:00: Lien Nguyen (Hanoi National University of Education, Vietnam)
    Title: Mittag - Leffler stability of mild solutions to Caputo fractional-order time-delay systems
    Abstract: In this talk, some classes of fractional - order time-delay systems described by Caputo fractional derivative in both linear and nonlinear cases are introduced. For the linear case, the concept of mild solutions, a type of integral solutions or generalized solutions, is presented and the existence and uniqueness of mild solutions is explored using the Banach fixed point theorem. Then, by utilizing the properties of Mittag - Leffler functions and novel comparison techniques, Mittag - Leffler stability of mild solutions is addressed. The proposed conditions are derived from both the spectral-type conditions and matrix inequality-type conditions. These results also can be extended naturally for a special nonlinear case, the homogeneous cooperative systems.

    11:00 - 12:00: Hong-Hai Ly (University of Ostrava, Czech Republic)
    Title: Spectral Convergence of Neumann Laplacian Perturbed by an Infinite Set of Curved Holes
    Abstract: We propose the novel spectral properties of the Neumann Laplacian in a two-dimensional bounded domain perturbed by an infinite number of compact sets with zero Lebesgue measure, so-called curved holes. These holes consist of segments or parts of curves enclosed in small spheres such that the diameters of holes tend to zero as the number of holes approaches infinity. Specifically, we rigorously demonstrate that the spectrum of the Neumann Laplacian on the perturbed domain converges to that of the original operator on the domain without holes under specific geometric assumptions and an appropriate selection of hole sizes. Furthermore, we derive sophisticated estimates on the convergence rate in terms of operator norms and estimate the Hausdorff distance between the spectra of the Laplacians.


  • Thursday 20.12.2023, SR 11.32

    • 11:00 - 12:00: Hong-Hai Ly (University of Ostrava, Czech Republic)
    Title: An Asymptotic Formula for Eigenvalues of the Neumann Laplacian in Domains with a Small Star-shaped Hole
    Abstract: In this talk, we present a spectral problem of the Laplace operator in a two-dimensional bounded domain perforated by a small arbitrary star-shaped hole and on the smooth boundary of which the Neumann boundary condition is imposed. It is proved that the eigenvalues of this problem converge to the eigenvalues of the Laplacian defined on the unperturbed domain as the size of the hole approaches zero. Furthermore, our main theorem provides the rate of convergence by showing an asymptotic expansion for all simple eigenvalues with respect to the size and shape of the hole.