Уважаемые коллеги, 

В следующуй четверг 15 июня в 17:00 в аудитории Ц-25 состоится научный семинар, на котором выступит 

Sergey Maslov (University of Illinois at Urbana-Champaign, USA) 

Population Dynamics of Phage-Bacterial Ecosystems: Kill-the-Winner, Kill-the-Loser, and Kill-the-King 

I will present two simple "bottom-down" models that we recently proposed and studied [1,2]. The dynamic Kill-the-Winner model [2] suggests a mechanism explaining high species diversity in microbial ecosystems exposed to predation by phages. These systems are traditionally described in terms of the static equilibrium state of Lotka-Volterra equations in which bacterial growth is exactly balanced by losses due to phage predation. Here we consider a more dynamic scenario in which phage infections give rise to abrupt and severe collapses of bacterial populations whenever they become sufficiently large. Consequently, each bacterial population in our model follows cyclic dynamics of exponential growth interrupted by sudden declines. The combined population of all species/strains stays approximately constant making cycles of individual strains cryptic. While some of the species in our model are driven towards extinction, a finite number of the fastest growing species survives. Thus, in general the ecosystem diversity remains high. The number of surviving species is inversely proportional to the variation in their growth rates but increases with the frequency and severity of phage-induced collapses. Thus counter-intuitively we predict that microbial communities exposed to more violent perturbations should have higher diversity. 

[1] Maslov S, Sneppen K (2015) Diversity waves in collapse-driven population dynamics, PLoS Comput Biol 11: e1004440.
[2] Maslov S, Sneppen K (2017) Population cycles and species diversity in dynamic Kill-the-Winner model of microbial ecosystems, Scientific Reports 7, 39642 (bioRxiv: http://dx.doi.org/10.1101/067124) 

Приглашаются все желающие. Если кто-то хочет побеседовать с проф. Масловым индивидуально, пожалуйста, сообщите мне об этом. 

Уважаемые коллеги,

В следующую среду 24 мая в 13:30 в аудитории 2-28 состоится научный семинар, на котором выступит

Satya Majumdar (LPTMS, University Paris 11, France)

Diffusion with stochastic resetting

We study a simple model of search where the searcher undergoes normal diffusion, but once in a while resets to its initial starting point stochastically with rate $r$. The effect of a finite resetting rate r turns out to be rather drastic. First, the position of the walker approaches a nonequilibrium stationary state at long times. The approach to the stationary state is accompanied by an interesting `dynamical' phase transition. For searching an immobile target, resetting leads to finite mean search time which, as a function of r, has a minimum at an optimal resetting rate $r^*$. This makes the search process efficient. We then consider various generalizations of this simple resetting model: to Levy flights, to multiple walkers and also to spatially extended system such as fluctuating interfaces.

Приглашаются все желающие. Если кто-то хочет побеседовать с проф. Маджумдаром после его доклада, пожалуйста, сообщите мне об этом.

Кроме того, обращаю ваше внимание на то, что 22-23 мая в помещении лаборатории им. Понселе (Б. Власьевский пер., 11) С. Маджумдаром и Г. Шером будет прочитан мини-курс "Random matrices and extreme value statistics" (http://www.poncelet.ru/event/random-matrices-and-extreme-value-statistics). Вход свободный, приглашаются все желающие.

Уважаемые сотрудники,

15 мая (пятница) в 09-30 в аудитории Ц-25 состоится собрание кафедры.

Уважаемые сотрудники,

14 аперля (пятница) в 09-30 в аудитории Ц-25 состоится собрание кафедры.