Can cosmological perturbations produce early universe vorticity?
  In this special issue article, based on the talk with the same title in
session B5 (Theoretical and Mathematical Cosmology) at GR19, we review the case
of vorticity generation in cosmology using cosmological perturbation theory. We
show that, while at linear order the vorticity evolution equation has no source
term in the absence of anisotropic stress, at second order vorticity is sourced
by gradients in entropy and energy density perturbations. We then present some
estimates for the magnitude and scale dependence of the vorticity power
spectrum using simple input power spectra for the energy density and entropy
perturbations. Finally, we close with possible directions for future work
followed by some hints toward the observational importance of the vorticity so
generated, and the possibility of primordial magnetic field generation.
