BPCPPDYSOE21 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 9: Statistical Physics 2 - organized by Barbara Drossel (Darmstadt), Sabine Klapp (Berlin) und Thomas Speck (Mainz)
DY 9.2: Vortrag
Montag, 22. März 2021, 11:20–11:40, DYb
Negative dissipation and instability in systems with distributed delay — •Sarah A.M. Loos1, Simon Hermann2, and Sabine H.L. Klapp3 — 1Universität Leipzig — 2Humboldt-Universität zu Berlin — 3Technische Universität Berlin
Many natural and artificial systems are subject to some sort of delay, which can be in the form of a single discrete delay or distributed over a range of times. Here, we discuss the impact of this distribution on (thermo-)dynamical properties of time-delayed stochastic systems. To this end, we study a simple model with white and colored noise, and focus on the class of Gamma-distributed delays which includes a variety of distinct delay distributions typical for feedback experiments and biological systems. A physical application is a colloid subject to time-delayed feedback control, which is, in principle, experimentally realizable by co-moving optical traps. We uncover several unexpected phenomena in regard to the system's linear stability and its thermodynamic properties. First, increasing the mean delay time can destabilize, or stabilize the process, depending on the distribution of the delay. Second, for all considered distributions, the heat dissipation of the controlled system (e.g., the colloidal particle) can become negative, which implies that the delay force extracts energy of the heat bath. This refrigerating effect is particularly pronounced for exponential delay. The exponential delay further yields the largest stable parameter regions. In this sense, exponential delay represents the most effective and robust type of delayed feedback.