Two papers from researchers in the Condensed Matter Group have appeared in a single issue of one of the top physics journals, the Physical Review Letters.
In the first paper, Edinburgh scientists (Pierre Ballesta, Rut Besseling, Lucio Isa and Wilson Poon) collaborated with a Cretan colleague (George Petekidis) in an experimental study of the flow of concentrated suspensions in a ‘rheometer’ – a standard device for measuring the mechanical properties of many substances. The novelty here is that the Edinburgh team has built a unique instrument (see picture) to look through the sample as its properties were being determined. This led to the discovery of certain unexpected features in the way samples ‘slip’ on the walls of the measuring compartment. If such slip is not understood and properly accounted for, rheometric measurements will yield wrong results. Interestingly, the way suspensions of hard particles ‘slip’ appears totally different from the way suspensions of soft spheres do it, the latter having already been studied by Steve Meeker (who started his research career in Edinburgh) and Michel Cloitre of the ESPCI in Paris.
In a second paper in the same issue, Edinburgh scientist Richard Blythe teamed up with colleagues in Manchester (Alan McKane) and Wellington (Gareth Baxter), New Zealand to explore theoretical connections between models used to describe apparently disparate phenomena: from species diversity in ecosystems through the way opinion changes in society to the evolution of language (illustrated in the schematic diagram). The common thread is that in all these cases, particular changes eventually get ‘fixated’. Blythe and his coauthors were able to derive an approximate expression for the average time taken to reach ‘fixation’ (or, in the case of opinion, consensus). Theirs results have direct application to current theories of language change.