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DY: Fachverband Dynamik und Statistische Physik

DY 7: Critical Phenomena and Phase Transitions

DY 7.1: Hauptvortrag

Montag, 18. März 2024, 11:30–12:00, BH-N 128

Critical transitions in non-autonomous complex dynamical systems: theory and applications to ecosystems and climate — •Ulrike Feudel — ICBM, Carl von Ossietzky Universität Oldenburg, Germany

Many systems in nature are characterized by the coexistence of different stable states for a given set of environmental parameters and external forcing. Examples for such behavior can be found in different fields of science ranging from mechanical or chemical systems to ecosystem and climate dynamics. Perturbations, applied to those natural systems can lead to a critical transition from one stable state to another. Such critical transitions -- also called tipping phenomena -- can happen in various ways: (1) due to bifurcations, i.e. changes in the dynamics when external forcing or parameters are varied extremely slow (2) due to fluctuations which are always inevitable in natural systems, (3) due to shocks or extreme events, and (4) due to rate-induced transitions, i.e. when external forcing changes too fast compared to the ability of the forced system to follow the changes. We discuss these critical transitions and their characteristics and illustrate them with examples from mechanical and natural systems. Special emphasis is given to non-autonomous systems, in which we highlight the interplay between different time scales, like the dissipative time scale and the time scale of the variation of parameters or forcing. Moreover, we discuss the role of unstable states, that are not directly observable in nature, but nevertheless act as the organizing centers of the dynamics.

Keywords: critical transitions; non-autonomous dynamics; time scale separation; climate; ecosystems