@article {2013, title = {Defect annihilation and proliferation in active nematics}, number = {arXiv:1303.4720;}, year = {2013}, note = {5 pages, 4 figures}, institution = {SISSA}, abstract = {Liquid crystals inevitably possess topological defect excitations generated\r\nthrough boundary conditions, applied fields or in quenches to the ordered\r\nphase. In equilibrium pairs of defects coarsen and annihilate as the uniform\r\nground state is approached. Here we show that defects in active liquid crystals\r\nexhibit profoundly different behavior, depending on the degree of activity and\r\nits contractile or extensile character. While contractile systems enhance the\r\nannihilation dynamics of passive systems, extensile systems act to drive\r\ndefects apart so that they swarm around in the manner of topologically\r\nwell-characterized self-propelled particles. We develop a simple analytical\r\nmodel for the defect dynamics which reproduces the key features of both the\r\nnumerical solutions and recent experiments on microtuble-kinesin assemblies.}, url = {http://hdl.handle.net/1963/6566}, author = {Luca Giomi and Mark J. Bowick and Xu Ma and M. Cristina Marchetti} }