The Physics of Flocking: From Cells to Crowds

Coordinators: Cristina Marchetti

Birds flock! It is just one of the many remarkable examples of collective behavior found in nature. Physicists have been able to capture some of this behavior by modeling birds as tiny, flying magnetic spins that align with their neighbors according to simple rules. Thanks to these successes, flocking has become a paradigm for the behavior of living and non-living systems where a large number of individually driven units exhibit coherent organization at larger scales. Such systems include suspensions of swimming bacteria, layers of migrating cells, long biopolymers driven by proteins in the cell cytoskeleton and collections of synthetic microswimmers.  Physicists, biologists and mathematicians are using statistical physics to model the complex behavior of these systems and to identify unifying principles. 

This Teachers' Conference, which will take place in conjunction with the interdisciplinary KITP program on "Active Matter: Cytoskeleton, Cells, Tissues and Flocks", is intended to introduce high-school science teachers to this rapidly developing field by presenting examples of dynamical organization at various scales, from the complex hierarchical structures found inside cells, to the coordinated patterns of behavior of groups of animals.


  • Andrew Bernoff, the Diana and Kenneth Jonsson Professor, and chair of the Department of Mathematics at Harvey Mudd College, will speak on "Synchronization and Swarming of Clocks and Flocks." As befits an applied mathematician, he has applied his mathematical skills to many diverse areas, including the collective behavior of insects such as aphids and locusts.  He has recently co-authored an extensive primer on swarm equilibria in the main journal of the Society for Industrial and Applied Mathematics (SIAM Review).  He is passionate about undergraduate education, mentoring undergraduate research, and helping students find careers and pursue graduate studies in applied mathematics.
  • Jeffrey Guasto, Assistant Professor of Mechanical Engineering at Tufts University, will speak on "The acrobatics of swimming bacteria". He uses experimental methods, mainly microfluidics and high-speed imaging, to understand the dynamics of swimming microorganisms, such as bacteria and sperm cells. His recent work on marine microbes has been featured in an article by the MIT News Office.
  • Cristina Marchetti, the William R. Kenan Professor of Physics at Syracuse University and the Associate Director of the Syracuse Biomaterials Institute, will speak on 'Living' matter. She is a theorist interested in understanding the emergent behavior of soft and biological materials, from layers of vibrated grains to bacterial suspensions, the cell cytoskeleton and living tissues.
  • Xavier Trepat, a Group Leader at IBEC, the Institute for Bioengineering of Catalonia in Barcelona, Spain, will speak on "Physical forces that drive cells". His work on the mechanical forces that control the organized migration of cells and tissues is beginning to inform our understanding of important biological functions, such as wound healing, morphogenesis, and collective cell invasion in cancer, and has recently been featured on the cover of the journal Nature Materials.