Coexistence of liquid and solid phases in flowing soft-glassy materials

Magnetic-resonance-imaging rheometrical experiments show that concentrated suspensions or emulsions cannot flow steadily at a uniform rate smaller than a critical value (gamma(c)). As a result, a "liquid" region (sheared rapidly, i.e., at a rate larger than gamma(c)) and a "solid" region (static) coexist. The behavior of the fluid in the liquid region follows a simple power-law model, while the extent of the solid region increases with the degree of jamming of the material.     

Viscous fingering in a yield stress fluid

A new Monte Carlo method for calculating ground-state properties of liquid 4He is described. It is shown that Bose-Einstein condensation (BEC) implies delocalization of the wave function. It is shown that there is no general connection between the static structure factor and BEC. It is suggested that the observed connection in liquid 4He is due to the creation of spaces in the liquid structure, which are required so that the wave function can delocalize, in the presence of the hard-core interactions. It is shown that this suggestion is quantitatively consistent with observations on liquid 4He.