# Prof. Dr. André Schlichting, Angewandte Mathematik Münster: Institut für Analysis und Numerik

Member of Mathematics MünsterInvestigator in Mathematics Münster

Investigator in Mathematics Münster

Research Interests | Nonlinear dynamics of partial/ordinary differential equations and stochastic processes long-time asymptotics: metastability, phase-transitions and coarsening Interacting particle system and their scaling limits Variational methods for evolution equations: gradient flows and optimal transport Structure preserving numerical schemes |

Project membershipMathematics Münster | C: Models and ApproximationsC1: Evolution and asymptotics C2: Multi-scale phenomena and macroscopic structures C3: Interacting particle systems and phase transitions |

Current Publications | • Navarro-Fernández V, Schlichting A Error estimates for a finite volume scheme for advection-diffusion equations with rough coefficients. ESAIM: Mathematical Modelling and Numerical Analysis Vol. 57 (4), 2023 online• Menz G, Schlichting A, Tang W, Wu T Ergodicity of the infinite swapping algorithm at low temperature. Stochastic Processes and their Applications Vol. 151, 2022, pp 1-34 online• Niethammer Barbara, Pego Robert L., Schlichting André, Velázquez Juan J. L, Oscillations in a Becker-Döring model with injection and depletion. SIAM Journal on Applied Mathematics Vol. 82 (4), 2022 online• Navarro-Fernández V, Schlichting A, Seis C Optimal stability estimates and a new uniqueness result for advection-diffusion equations. Pure and Applied Analysis Vol. 4 (3), 2022 online• Peletier Mark A., Schlichting André Cosh gradient systems and tilting. Nonlinear Analysis: Theory, Methods and Applications Vol. 2203, 2022 online• Esposito A, Patacchini F, Schlichting A, Slepčev D Nonlocal-interaction equation on graphs: gradient flow structure and continuum limit. Arch. Ration. Mech. Anal. Vol. 2021, 2021 online• Eichenberg C, Schlichting A Self-similar behavior of the exchange-driven growth model with product kernel. Commun. Partial. Differ. Equ. Vol. 46 (3), 2021 online• Schlichting André, Seis Christian The Scharfetter–Gummel scheme for aggregation–diffusion equations. IMA Journal of Numerical Analysis Vol. 42 (3), 2021 online• Esposito A, Gvalani RS, Schlichting A, Schmidtchen M On a novel gradient flow structure for the aggregation equation. Preprint arXiv:2112.08317 Vol. 2021, 2021 online |

Current Projects | • EXC 2044 - C1: Evolution and asymptotics In this unit, we will use generalisations of optimal transport metrics to develop gradient flow descriptions of (cross)-diffusion-reaction systems, rigorously analyse their pattern forming properties, and develop corresponding efficient numerical schemes. Related transport-type- and hyperbolic systems will be compared with respect to their pattern-forming behaviour, especially when mass is conserved. Bifurcations and the effects of noise perturbations will be explored.Moreover, we aim to understand defect structures, their stability and their interactions. Examples are the evolution of fractures in brittle materials and of vortices in fluids. Our analysis will explore the underlying geometry of defect dynamics such as gradient descents or Hamiltonian structures. Also, we will further develop continuum mechanics and asymptotic descriptions for multiple bodies which deform, divide, move, and dynamically attach to each other in order to better describe the bio-mechanics of growing and dividing soft tissues. Finally, we are interested in the asymptotic analysis of various random structures as the size or the dimension of the structure goes to infinity. More specifically, we shall consider random polytopes and random trees.For random polytopes we would like to compute the expected number of faces in all dimensions, the expected (intrinsic) volume, and absorption probabilities, as well as higher moments and limit distributions for these quantities. online • EXC 2044 - C2: Multi-scale phenomena and macroscopic structures In multi-scale problems, geometry and dynamics on the micro-scale influence structures on coarser scales. In this research unit we will investigate and analyse such structural interdependence based on topological, geometrical or dynamical properties of the underlying processes.We are interested in transport-dominated processes, such as in the problem of how efficient a fluid can be stirred to enhance mixing, and in the related analytical questions. A major concern will be the role of molecular diffusion and its interplay with the stirring process. High Péclet number flow in porous media with reaction at the surface of the porous material will be studied. Here, the flowinduces pore-scale fluctuations that lead to macroscopic enhanced diffusion and reaction kinetics. We also aim at understanding advection-dominated homogenisation problems in random regimes. We aim at classifying micro-scale geometry or topology with respect to the macroscopic behaviour of processes considered therein. Examples are meta material modelling and the analysis of processes in biological material. Motivated by network formation and fracture mechanics in random media, we will analyse the effective behaviour of curve and free-discontinuity energies with stochastic inhomogeneity. Furthermore, we are interested in adaptive algorithms that can balance the various design parameters arising in multi-scale methods. The analysis of such algorithms will be the key towards an optimal distribution of computational resources for multi-scale problems. Finally, we will study multi-scale energy landscapes and analyse asymptotic behaviour of hierarchical patterns occurring in variational models for transportation networks and related optimal transport problems. In particular, we will treat questions of self-similarity, cost distribution, and locality of the fine-scale pattern. We will establish new multilevel stochastic approximation algorithms with the aim of numerical optimisation in high dimensions. online • EXC 2044 - C3: Interacting particle systems and phase transitions The question of whether a system undergoes phase transitions and what the critical parameters are is intrinsically related to the structure and geometry of the underlying space. We will study such phase transitions for variational models, for processes in random environments, for interacting particle systems, and for complex networks. Of special interest are the combined effects of fine-scalerandomly distributed heterogeneities and small gradient perturbations.We aim to connect different existing variational formulations for transportation networks, image segmentation, and fracture mechanics and explore the resulting implications on modelling, analysis, and numerical simulation of such processes. We will study various aspects of complex networks, i.e. sequences of random graphs (Gn)n∈N, asking for limit theorems as n tends to infinity. A main task will be to broaden the class of networks that can be investigated, in particular, models which include geometry and evolve in time. We will study Ising models on random networks or with random interactions, i.e. spin glasses. Fluctuations of order parameters and free energies will be analysed, especially at the critical values where the system undergoes a phase transition. We will also investigate whether a new class of interacting quantum fields connected with random matrices and non-commutative geometry satisfies the Osterwalder-Schrader axioms. Further, we will study condensation phenomena, where complex network models combine the preferential attachment paradigm with the concept of fitness. In the condensation regime, a certain fraction of the total mass dynamically accumulates at one point, the condensate. The aim is a qualitative and quantitative analysis of the condensation. We willalso explore connections to structured population models. Further, we will study interacting particle systems on graphs that describe social interaction or information exchange. Examples are the averaging process or the Deffuant model. We will also analyse asymmetric exclusion processes (ASEP) on arbitrary network structures. An interesting aspect will be how these processes are influenced by different distribution mechanisms of the particles at networks nodes. If the graph is given by a lattice, we aim to derive hydrodynamic limits for the ASEP with jumps of different ranges for multiple species, and for stochastic interactingmany-particle models of reinforced random walks. Formally, local cross-diffusion syste ms are obtained as limits of the classical multi-species ASEP and of the many-particle random walk. We will compare the newly resulting limiting equations and are interested in fluctuations, pattern formation, and the long-time behaviour of these models on the microscopic and the macroscopic scale. Further, we will analyse properties of the continuous directed polymer in a random environment. online |

E-Mail | a.schlichting@uni-muenster.de |

Phone | +49 251 83-35091 |

Room | 130.026 |

Address | Prof. Dr. André Schlichting Angewandte Mathematik Münster: Institut für Analysis und Numerik Fachbereich Mathematik und Informatik der Universität Münster Orléans-Ring 10 48149 Münster |

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