Numerical evidence of nonuniqueness in the evolution of vortex sheets Milton C. Lopes Filho, John Lowengrub, Helena J. Nussenzveig Lopes and Yuxi Zheng ESAIM: M2AN, 40 2 (2006) 225-237 Published online: 21 June 2006 DOI: 10.1051/m2an:2006012