Instability of point defects in a two-dimensional nematic liquid crystal model

We study a class of symmetric critical points in a variational 2D Landau-de Gennes model where the state of nematic liquid crystals is described by symmetric traceless 3 x 3 matrices. These critical points play the role of topological point defects carrying a degree k/2 for a nonzero integer k. We prove existence and study the qualitative behavior of these symmetric solutions. Our main result is the instability of critical points when vertical bar k vertical bar >= 2. (C) 2015 Elsevier Masson SAS. All rights reserved.