13.05.2024 16:30 Stein Andreas Bethuelsen: Mixing for Poisson representable processes and the contact process
In this talk I will present some new insights on so-called Poisson representable processes, a general class of {0,1}-valued processes recently introduced by Forsström, Gantert and Steif. Particularly, I will discuss a new characteristic of these in terms of certain mixing properties. As an application thereof, I will argue that the upper invariant measure of the contact process on Z^d is not Poisson representable, thereby answering a question raised in the above mentioned work. This relies on the upper invariant measure satisfying certain directional mixing properties, but not their spatial equivalent. Moreover, the general approach extends to other processes having similar properties, such as the plus phase of the Ising model on Z^2 in the phase transition regime.
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27.05.2024 16:30 Julius Hallmann: Asymptotic Analysis of Randomized Epidemic Processes
This talk is concerned with the following epidemic process: A set of nodes is partitioned into three states: susceptible, infectious, and recovered. We start with a single infectious node. Proceeding in rounds whose length is antiproportional to the population size, a fixed amount of nodes are drawn independently at random. If at least one of the selected nodes is infectious, every susceptible node in the sample becomes infected. Moreover, any infectious vertex recovers independently at a constant rate. If the expected amount of infections caused by single node is less than one, the epidemic dies out quickly and leaves almost the entire population untouched. If it is above one, either the infection dies out quickly or a large outbreak occurs, during which a non-vanishing fraction of the population is affected. Moreover, if enough nodes are infectious at the same time, the system’s behaviour is essentially deterministic.
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