Dresden 2017 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 18: Brownian Motion / Noise (joint session DY/TT)

DY 18.4: Vortrag

Dienstag, 21. März 2017, 10:45–11:00, ZEU 147

Dynamically Crowded Solutions of Brownian Needles — •Sebastian Leitmann1, Felix Höfling2, and Thomas Franosch11Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21A, A-6020 Innsbruck, Austria — 2Fachbereich Mathematik und Informatik, Freie Universität Berlin, Arnimallee 6, 14195 Berlin, Germany

We perform Brownian dynamics simulations of solutions of infinitely thin needles up to densities n deep in the semidilute regime. With increasing density, the motion of a needle becomes increasingly restricted to a sliding back-and-forth movement in a tube composed of the surrounding needles. From the density-dependent behavior of the rotation and the translation we extract the corresponding longtime transport coefficients and corroborate the scaling behavior of ∼ n−2. The characteristic algebraic decay of ∼ t−1/2 in the intermediate scattering function and a plateau over many decades in time in the non-Gaussian parameter represent a fingerprint of the sliding motion of the needle within the tube. We show that on coarse-grained time and length scales, the dynamics of a needle in solution is captured by a single needle (phantom needle) with the extracted transport coefficients as input parameters [1] as anticipated from the tube theory of Doi and Edwards [2]. We also compare the dynamics to needle Lorentz systems where a single tracer needle explores a quenched array of other needles.

[1] S. Leitmann, F. Höfling, and T. Franosch, Phys. Rev. Lett. 117, 097801 (2016). [2] M. Doi and S. F. Edwards, J. Chem. Soc., Faraday Trans. 2 74, 560 (1978).

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