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Wednesday, 27.10.2021, 11:30 (Online Event)

Seminar Interacting Random Systems
András Tóbiás, TU Berlin:
Virus dynamics in the presence of contact-mediated host dormancy (online talk)
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Online Event

Abstract
Abstract: We investigate a stochastic individual-based model for the population dynamics of host-virus systems where the hosts may transition into a dormant state upon contact with virions, thus evading infection. Such a dormancy-based defence mechanism was described in Bautista et al (2015). We first analyse the effect of the dormancy-related model parameters on the probability of invasion of a newly arriving virus into a resident host population. It turns out that the probability of dormancy initiation upon virus contact plays a crucial role, while the lengths of the dormancy periods or the death rate during dormancy are largely irrelevant. Given successful invasion, we then show that the emergence of a persistent virus infection ('epidemic') in the host population corresponds to the existence of a coexistence equilibrium for the deterministic many-particle limit of our model. In this context, all dormancy-related parameters have a significant impact. Indeed, while related systems without recovery of infected individuals and dormancy may exhibit a Hopf bifurcation, giving rise to a variant of the 'paradox of enrichment', we provide simulations and rigorous partial results showing that the inclusion of dormancy and recovery can prevent this loss of stability. Finally, we show that the presence of contact-mediated dormancy enables the host population to maintain higher equilibrium sizes (resp. fitness values) - while still being able to avoid a persistent epidemic - than host populations without this trait, for which high fitness values would imply a high risk for the emergence of a persistent epidemic. This adds a twist to the relevance of 'reproductive trade-offs' usually associated with costly dormancy traits. The subject of this talk is joint work with Jochen Blath.

Further Informations
Seminar Interacting Random Systems (Online Event)

Host
WIAS Berlin

Wednesday, 27.10.2021, 15:15 (Online Event)

Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Matthias Liero, WIAS Berlin:
Electrothermal drift-diffusion models for organic semiconductor devices (online talk)
more ... Location
Online Event

Further Informations
Berliner Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)

Host
Humboldt-Universität zu Berlin
WIAS Berlin

Wednesday, 03.11.2021, 10:00 (Online Event)

Forschungsseminar Mathematische Statistik
Prof. Evgeny Stepanov, Russian Academy of Sciences, Russische Föderation:
The story of a fish in a turbulent ocean: How to survive and how to return home
more ... Location
Online Event

Abstract
Can a fish with limited velocity capabilities reach any point in the (possibly unbounded) ocean? In a recent paper by D. Burago, S. Ivanov and A. Novikov, “A survival guide for feeble fish", an affirmative answer has been given under the condition that the fluid velocity field is incompressible, bounded and has vanishing mean drift. This brilliant result extends some known point-to-point global controllability theorems though being substantially non constructive. We will give a fish a different recipe of how to survive in a turbulent ocean, and show how this is related to structural stability of dynamical systems by providing a constructive way to change slightly a divergence free vector field with vanishing mean drift to produce a non dissipative dynamics. This immediately leads to closing lemmas for dynamical systems, in particular to C. Pugh's closing lemma, saying also that the fish can eventually return home. Joint work with Sergey Kryzhevich (St. Petersburg).

Further Informations
Forschungsseminar Mathematische Statistik

Host
Humboldt-Universität zu Berlin
WIAS Berlin