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The Physics & Astronomy Colloquium Series presents Sonya Bahar of Center for Neurodynamics and University of Missouri at St. Louis, discussing “Phase Transitions in Evolutionary and Population Dynamics" on Jan. 14.


Colloquia are Fridays at 4:10 p.m.



Abstract: Understanding the mechanisms of population collapse and evolutionary dynamics are critically important both for rescuing at-risk species as climate change accelerates, and for mapping the underlying patterns of evolutionary history. Studies of bacterial population collapse also have important implications for the increasing problem of antibiotic resistance.


I will discuss applications of the statistical physics of nonequilibrium phase transitions (1) to computational models of evolutionary dynamics and (2) in experimental studies of microbial populations. In the computational studies, we find that simulated populations undergo a phase transition from survival to extinction as various control parameters are varied. This transition has some characteristics of directed percolation, but does not completely fall into that universality class. Experimentally, we find that microbial populations respond to some stressors with phase-transition-like collapse, and to other stressors with more graduate decline. Yeast cells (S. cerevisiae), for example, exhibit phase-transition-like behavior in the presence of heat stress, but a gradual decline in the presence of salt stress. Surprisingly, bacterial (E. coli) populations show such differential responses even to antibiotics with similar mechanisms of action.

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  • Gregory Leblanc

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