Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - International Research Training Group 1740

Seminar Talk - P. Radtke - J. Kromer

  • Wann 02.07.2014 von 15:00 bis 16:00
  • Wo New 15, R 3'101
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Seminar Talk

Paul Radtke (Humboldt-Universität zu Berlin, Project B06)

Title: Dynamics of a bipolar field memristor

The ‘memory resistor’ or memristor is a nonlinear electric circuit element whose resistance does not remain constant but depends on the history of the system. Proposed due to symmetry considerations by L. Chua in 1971, it was not experimentally realized until 2008. Together with the resistor, the capacitor and the inductor it encompasses the basic passive circuit elements. Possible applications include the replacement of RAM (random-access memory) with nonvolatile resistive RAM.
We will show that a lattice model with hopping ions agited by an external field reproduces the memristor effect and how by the help of a Burgers equation the underlying dynamics of oxygens vacancies can be interpreted the oxygen vacancies as nonlinear traveling waves. However, this model does not constitute an ideal memristor. Based on an adapted ideal memristor model, reasons for this divergence are suggested.

Justus Kromer (Humboldt-Universität zu Berlin, Project B07)

Title: Noise-controlled metastability in an excitable system with positive feedback

We study the effect of event-triggered positive feedback on a stochastic phase oscillator model operating in the excitable regime. If a noisy excitation leads to an excursion from the stable node, a slow-decaying feedback is applied that pushes the system closer to the oscillatory regime.
In addition to the low-activity excitable state, strong feedback can cause a self-driving effect, i.e. once excursions occur at a high rate the feedback stabilizes the system in a high-activity oscillatory state.
Furthermore, we investigate the role of noise in such systems. Interestingly, noise not only leads to transitions between those metastable states but also controls their occupation probability. As a consequence, noise can be used to tune system properties like variability, which possess giant values for equiprobable states.