Complex-space singularities of 2D Euler flow in Lagrangian coordinates

We show that, for 2D space-periodic incompressible flow, the solution can be evaluated numerically in Lagrangian coordinates with the same accuracy that is achieved in standard Eulerian spectral methods. This allows the determination of complex-space Lagrangian singularities. Lagrangian singularities are found to be closer to the real domain than Eulerian singularities and seem to correspond to fluid particles which escape to (complex) infinity by the current time. Various mathematical conjectures regarding Eulerian/Lagrangian singularities are presented.