Jeferson J. Arenzon

We study the two-dimensional domain morphology of twisted nematic liquid crystals during their phase-ordering kinetics [R. A. L. Almeida, Phys. Rev. Lett. 131, 268101 (2023)], which is a physical candidate to self-generate critical clusters in the percolation universality class. Here, we present experimental evidence that large clusters and their hulls are indeed both fractals with dimensions of the corresponding figures in critical percolation models.

We introduce a minimal model of multilevel selection on structured populations, considering the interplay between game theory and population dynamics. Through a bottleneck process, finite groups are formed with cooperators and defectors sampled from an infinite pool. After the fragmentation, these transient compartments grow until the maximal number of individuals per compartment is attained. Eventually, all compartments are merged and well mixed, and the whole process is repeated.