HEDGEHOG ANNIHILATION IN A CONFINED NEMATIC LIQUID CRYSTAL M. Svetec and Z. Bradac ˇ Laboratory of Physics of Complex Systems, Faculty of Education, University of Maribor, Koro ska 160, 2000 Maribor, Slovenia S. Kralj Laboratory of Physics of Complex Systems, Faculty of Education, University of Maribor, Koro ska 160, 2000 Maribor, Slovenia and Joz ˇef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia S. Z ˇ umer Joz ˇef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia and Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia Annihilation of a pair of nematic point defects, having opposite strength is studied numerically. The defects are enclosed within an infinite cylindrical cavity whose lateral wall enforces strong homeotropic anchoring. The Lebwohl-Lasher lattice model is used. The dynamics of the system consisting of N > 10 5 molecules is studied using the Brownian molecular dynamics. We study pre-collision, collision and post-collision regimes. In the first regime the defects are well separated and are clearly distinguishable. Latter the core structures of defects strongly overlap and gradually decay into the defectless state. Keywords: annihilation; nematic liquid crystal; nucleation; point defects This research was supported by the ESF network project COSLAB and Slovenian Office of Science (PO-0524-0106). Address correspondence to M. Svetec, Laboratory of Physics of Complex Systems, Faculty of Education, University of Maribor, Koro ska 160, 2000 Maribor, Slovenia. 43=[2179] Mol. Cryst. Liq. Cryst., Vol. 413, pp. 43=[2179]–51=[2187], 2004 Copyright # Taylor & Francis Inc. ISSN: 1542-1406 print=1563-5287 online DOI: 10.1080=15421400490432551