Dresden 2020 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 24: Complex Fluids and Soft Matter (joint session DY/CPP)

DY 24.3: Talk

Tuesday, March 17, 2020, 10:00–10:15, ZEU 160

Relations between angular and Cartesian orientational expansions* — •Michael te Vrugt and Raphael Wittkowski — Institut für Theoretische Physik, Center for Soft Nanoscience, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany

Orientational expansions, which are widely used in the natural sciences, exist in angular and Cartesian form. Although these expansions are orderwise equivalent, it is difficult to relate them in practice. Moreover, the standard expansion has to be modified for particles with asymmetric shape, where a description in terms of spherical harmonics or symmetric traceless tensors is not sufficient. We discuss various methods for orientational expansions and their application for the definition of orientational order parameters in liquid crystal physics. In particular, we explain how conversion tables between angular and Cartesian expansions can be constructed, which we have done up to third order. This is important, e.g., for the comparison of theoretical and experimental results in liquid crystal physics.
*Funded by the Deutsche Forschungsgemeinschaft (DFG) – WI 4170/3-1