Intensive lecture at Tohoku Univ. "Physics of Active Matter"
Dates and Times
June 5 (Mon), 2023
14:40-16:10 Lecture 1 "Introduction to active matter & self-propelled particles"
16:20-17:50 Lecture 2 "Flocking state and phase transition thereto"
June 6 (Tue), 2023
13:00-14:30 Lecture 3 "Motility-induced phase separation"
14:40-16:10 Lecture 4 "Active liquid crystal"
16:20-17:50 Colloquium "Glassy state of active matter and its realization in bacterial populations"
Active matter is "matter made of non-equilibrium molecules", that is a collection of particles that behave and interact in a non-equilibrium manner, often being self-propelled particles inspired by living organisms and cells. Decades of studies have witnessed various "phases" of active matter, including active gas, active fluid and active liquid crystal, and characterized these phases as well as phase transitions and phase separations of active matter. The goal of the lecture is to understand the basics of active matter, such as what active matter is, what are characteristic phenomena and properties, and how these can be described theoretically.
The password to open the files will be announced in the lecture
An interesting question in active matter physics is what states of matter may arise in active matter and how different they are from thermal systems. This, in the case of glassy states of matter, is what I want to discuss in this Colloquium. After reviewing some characteristic properties of thermal glass and existing studies on active glass, I will present our recent experimental finding of an active glass state in populations of swimming bacteria, namely Escherichia coli. Unlike thermal glass, bacteria may grow and divide in a nutrient-rich condition and spontaneously transition to a glassy state. Interestingly, this takes place in two steps, the first one suppressing only the orientational degrees of freedom, and the second one vitrifying the population completely. Characterizing statistical properties of this bacterial glass, we find both similarities and dissimilarities compared with thermal glass. The latter include anomalous signals in the dynamic susceptibility and an unusual value of a power-law exponent hinting at non-equilibrium nature of the transition. I will also describe the relevance of such dense populations of bacteria in nature and in our lives.