Berlin 2015 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 61: Focus: Disordered Systems, Glasses under Shear I (joint session CPP, DY)

CPP 61.5: Hauptvortrag

Donnerstag, 19. März 2015, 10:45–11:15, C 243

Dense granular flow — •Annette Zippelius — Institut für Theo. Physik, Univ. Göttingen, Friedrich-Hund Platz 1, 37077 Göttingen

In the first part of the talk I will discuss a jamming scenario of frictional particles, which can be interpreted as a nonequilibrium first order phase transition (1). Results of numerical simulations will be presented and analyzed in the framework of a simple model which can account for both, the continuous frictionless case and the discontinuous frictional case. The most important features of the frictional phase diagram are reentrant behaviour and a critical jamming point at finite stress.

The second topic to be discussed are dynamical heterogeneities and scaling in a driven granular fluid as structural arrest is approached (2). Large scale simulations of 2d bidisperse granular fluids allow us to determine spatial correlations of slow particles via the four-point structure factor. As the fluid approaches structural arrest, scaling is shown to hold. Both the dynamic susceptibility as well as the dynamic correlation, evaluated at the alpha-relaxation time,can be fitted to a power law divergence at a critical packing fraction. The measured susceptibility widely exceeds the largest one previously observed for hard sphere 3d fluids. The clusters of slow particles are neither compact nor stringlike but fractal. The cluster size distrbution is shown to fall off algebraically as structural arrest is approached.

(1) M. Grob, C. Heussinger and A. Zippelius, Phys. Rev E 89, 050201 (R) (2014); (2) K. Avila, H. C. Castill, A. Fiege, K. Vollmayr-Lee and A.Zippelius, Phys. Rev. Lett. 113, 025701 (2014)