Abstract:
Liquid crystals with negative anisotropic dielectric constant and homeotropic anchoring are a natural physical context where dissipative vortices are observed. Dissipative vortices are known in this context as \emph{umbilical defects}.Major problems arise when practical implementations are aimed at, because soft-matter defects are dissipative structures that obey a complex Ginzburg-Landau equation (CGLE) and undergo a coarsenig dynamics ruled by their mutual interaction and annhilation. Therefore, they are unstable, usually limited to a single defect pair per sample or a defect-free sample, and without the possibility of controlled addressing. We present a method of controlled generation of a vortex triplet by means of an inhomogeneous magnetic field generated by a Neodymium magnet ring. Using an amplitude equation that describes the system close to the Fredererickzs transition allows to characterize analytically the triplet. Numerical simulations show quite good agreement with analytical results and experimental observations.