Click here to flash read.
Topological defects, which are singular points in a director field, play a
major role in shaping active systems. Here, we experimentally study topological
defects and the flow patterns around them, that are formed during the highly
rapid dynamics of swarming bacteria. The results are compared to the
predictions of two-dimensional active nematics. We show that, even though some
of the assumptions underlying the theory do not hold, the swarm dynamics is in
agreement with two-dimensional nematic theory. In particular, we look into the
multi-layered structure of the swarm, which is an important feature of real,
natural colonies, and find a strong coupling between layers. Our results
suggest that the defect-charge density is hyperuniform, i.e., that long range
density-fluctuations are suppressed.
No creative common's license