Democratic particle motion for meta-basin transitions in simple   glass-formers
  We use molecular dynamics computer simulations to investigate the local motion of the particles in a supercooled simple liquid. Using the concept of the distance matrix we find that the alpha-relaxation corresponds to a small number of crossings from one meta-basin to a neighboring one. Each crossing is very rapid and involves the collective motion of O(40) particles that form a relatively compact cluster, whereas string-like motions seem not to be relevant for these transitions. These compact clusters are thus candidates for the cooperatively rearranging regions proposed long times ago by Adam and Gibbs. 
G. A. Appignanesi (Laboratorio de Fisicoquimica, Bahia Blanca), J. A.   Rodriguez Fris (Laboratorio de Fisicoquimica, Bahia ...