SFI Seminar: ‘The Secret Life of Active Colloids’

Gabriel Redner

SFI News:

The Santa Fe Institute will host a seminar at 12:15 p.m. Tuesday, Sept. 2 in the Collins Conference Room, 1399 Hyde Park Road. Gabriel Redner, Brandeis University, will speak on “The Secret Life of Active Colloids.”


Active systems are composed of self-propelled units which interact to produce a wide range of complex behaviors. In this talk I will describe a minimalist active system comprised of self-propelled spheres immersed in a fluid and confined to two dimensions, interacting through hard-core repulsion alone. I will describe an unusual type of phase transition in which the system spontaneously separates into dense and dilute phases, even in the absence of any attractive interaction.

I will draw comparisons between this athermal active process and the behavior of ordinary fluids undergoing phase separation. When attraction is added to the active system, the system’s phase diagram becomes reentrant as a function of activity, with phase separation at low and high activity with a single-phase fluid in between. I will introduce a kinetic model which captures the main features of the phase behavior and describes how activity can act to both suppress and induce phase separation.

SFI Host: Sid Redner

The Santa Fe Institute is a nonprofit research center in Santa Fe. Its scientists collaborate across disciplines to understand the complex systems that underlie critical questions for science and humanity. The Institute is supported by philanthropic individuals and foundations, forward-thinking partner companies, and government science agencies.


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