Date/Time
Date(s) - 21/11/2022
11:30 am - 12:30 pm

Speaker:  Lee van Brussel (McMaster University)

Title: Topological defects for two-dimensional nematic liquid crystals

Abstract: In a naive sense, materials classified as `liquid crystal' retain some partial orientational ordering of their molecules (like solids) but are simultaneously capable of diffusing throughout their container (like liquids). One way to model such a material in two dimensions is to use an orientational order parameter given by an $mathbb{S}^1$-valued vector field called a director, which indicates the “averag'' direction of alignment of the molecules locally at some point in the sample. By using the Ginzburg-Landau energy as a toy model for this system, it turns out that energy minimizing director configurations are intimately related to the winding number of the molecular behaviour along the boundary and the winding behaviour about `defective regions' occurring in the material sample. Depending on the boundary conditions one imposes, these defective regions could occur in the interior of the material sample, and/or on the boundary. In this talk, I will provide experimental observations showing what these defective regions look like and how we relate the energy of the system to this winding behaviour.  

Location: Hamilton Hall 403