Liquid elasticity length, universal dynamic crossovers, and glass transition

We discuss two main universal dynamic crossovers in a liquid that correspond to relaxation times of 1 ps and 10−7–10−6 s. We introduce the concept of liquid elasticity length del. At room temperature, del is several Å in water and increases to 0.01 mm in honey and 1 mm in tar. We discuss that on temperature decrease, del = dm and del = L correspond to the two dynamic crossovers, where dm is the medium-range order and L is system size. In this picture, the two important changes in the dynamics of a system are defined by its fundamental lengths. The second crossover defines all kinetic aspects of the glass transition, whereas the 'thermodynamic' glass transition is realized in the limit of infinite system size only. In this picture, we also discuss the division of liquids into strong and fragile. One prediction of our theory is the increase of viscosity with the size of macroscopic system, which we verify by measuring the viscosity of honey.