A dense suspension of rod-like fd virus particles in a sealed sample tube
PHYSICS · Subjective · Fermi University Physics · Thermal, Statistical & Complex Systems · Condensed Matter, Materials & Soft Matter · Complex and collective systems
Many Parts, One Behaviour, Ch Emergence and self-organisation: collective order from local rules
Problem
A dense suspension of rod-like fd virus particles in a sealed sample tube, held at fixed temperature with no stirring, heating gradient or applied field, separates over several weeks into a cloudy isotropic region and a birefringent, ordered nematic region once the particle concentration exceeds a critical value.Someone argues: "Order has appeared here with no obvious external agent driving it, and it built up gradually over weeks with nothing pushing it from outside. That is exactly the situation with the heated oil layer that breaks into convection rolls, so this must be another case of self-organisation."Find the error in this argument, say what kind of ordering the nematic transition actually is, and name an observation on this sample (not the oil layer) that would settle the question, predicting what each kind of ordering would show.