abstract
- We show that a superconducting vortex in underdoped high T_c superconductors could have an antiferromagnetic core. This type of vortex configuration arises as a topological solution in the recently constructed SO(5) nonlinear sigma model and in Ginzburg-Landau theory with competing antiferromagnetic and superconducting order parameters. Experimental detection of this type of vortex by \mu SR and neutron scattering is proposed.