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Biomedical subjects

Knud Zabrocki

Publications and source records attributed to Knud Zabrocki.

2 recordsLinked to original sources

Memory driven Ginzburg-Landau model.

The time evolution of a bistable Ginzburg-Landau model (GL) with a non-Markovian memory term of strength lambda is studied. Due to the nonlinear feedback coupling, the two branches of the stationary solution are not only controlled by the sign of the initial condition P(0), but also by the strength and the sign of lambda. Whereas in case of a positive lambda the stationary solution is ever reduced through the memory, it may be increasing for lambda<0. In that case the system is also able to switch over between both branches of the stationary solution. Such an ability is exclusively achieved for a negative lambda within an interval -u<lambda<lambda(c), where lambda(c) is a critical memory strength and u is the strength of the conventional nonlinear term within the GL. The complete phase diagram is presented in the P(0)-lambda plane analytically and numerically.

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Evolution model with a cumulative feedback coupling.

The paper is concerned with a toy model that generalizes the standard Lotka-Volterra equation for a certain population by introducing a competition between instantaneous and accumulative, history-dependent nonlinear feedback the origin of which could be a contribution from any kind of mismanagement in the past. The results depend on the sign of that additional cumulative loss or gain term of strength lambda. In case of a positive coupling the system offers a maximum gain achieved after a finite time but the population will die out in the long time limit. In this case the instantaneous loss term of strength u is irrelevant and the model exhibits an exact solution. In the opposite case lambda<0 the time evolution of the system is terminated in a crash after t(s) provided u=0. This singularity after a finite time can be avoided if u not equal to 0. The approach may well be of relevance for the qualitative understanding of more realistic descriptions.

Journal Article↗