Regensburg 2019 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 43: Anomalous diffusion / Brownian motion

DY 43.11: Vortrag

Donnerstag, 4. April 2019, 12:45–13:00, H3

The cage effect in systems of hard spheres — •Hans Joachim Schöpe1 and William van Megen21Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10,72076 Tübingen, Germany — 2Department of Applied Physics, Royal Melbourne Institute of Technology, Melbourne, Victoria 3000, Australia

The cage effect is generally invoked when discussing the delay in the decay of time correlation functions of dense fluids. In an attempt to examine the role of caging more closely we consider the temporal evolution of the displacement distributions of Brownian particles. In an equilibrium fluid these distributions are necessarily biased by the presence of neighbouring particles. Accommodation of this bias by those neighbours conserves the displacement distribution locally and it presents a collective mechanism for exploring configuration space that is more efficient than the intrinsic Brownian motion. In contrast caging of some particles incurs a delayed, non-local collective transport process due to the fact that of the displacement distribution must be conserved globally. Both collective mechanisms incur delay or stretching of time correlation functions, in particular the particle number and flux densities [1]. We identify and distinguish these mechanisms in existing data from experiments [2,3] and computer simulations [4] on systems of particles with hard sphere interactions.

[1] J. Chem. Phys. 146, 104503 (2017) [2] Phys. Rev. Lett. 103 (25) (2009) [3] 4th International Symposium on Slow Dynamics in Complex Systems: Tohoku Univ, edited by M. Tokuyama and I. Oppenheim (2013), Vol. 1518, pp. 214-221 [4] Nature Comm. 5 (2014)

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