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SUMMARY:Extinctions under environmental noise - Tal Agranov (DAMTP)
DTSTART:20201117T130000Z
DTEND:20201117T140000Z
UID:TALK152545@talks.cam.ac.uk
CONTACT:Patrick Pietzonka
DESCRIPTION:Zoom link: https://maths-cam-ac-uk.zoom.us/j/94018037756\n\nTh
 e survival of natural populations may be greatly affected by environmental
  conditions that vary in space and time. \nWe look at a population residin
 g in two locations (patches) coupled by migration\, in which the local con
 ditions fluctuate in time. We report on two findings. First\, we find that
  unlike rare events in many other systems\, here the histories leading to 
 a rare extinction event are not dominated by a single path. We develop the
  appropriate framework\, which turns out to be a hybrid of the standard sa
 ddle-point method\, and the Donsker-Varadhan formalism which treats rare e
 vents of atypical averages over a long time. It provides a detailed descri
 ption of the statistics of histories leading to the rare event\, and the m
 ean time to extinction. The framework applies to rare events in a broad cl
 ass of systems driven by non-Gaussian noise.\nSecondly\, applying this fra
 mework to the population-dynamics model\, we find a novel phase transition
  in its extinction behavior. Strikingly\, a patch which is a sink (where i
 ndividuals die more than are born)\, can nonetheless reduce the probabilit
 y of extinction\, even if it normally lowers the population's size and gro
 wth rate.
LOCATION:via zoom\, meeting ID 940-1803-7756
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