Artificial-boundary conjecture for axisymmetric Euler blow-up

Consider smooth axisymmetric Euler solutions in the axisymmetric coordinate formulation, with vorticity non-vanishing on the axis of symmetry. Artificial-boundary conjecture. There exist such smooth solutions that become singular in finite time. The source explains that these solutions need not lift to smooth three-dimensional solutions on the symmetry axis, so the axis acts as an artificial boundary; the conjecture remains open.