Asymptotic properties of vortex-pair solutions for incompressible Euler equations in R2

A vortex pair solution of the incompressible 2d Euler equation in vorticity form
ωt+∇⊥Ψ⋅∇ω=0,Ψ=(−Δ)−1ω,in ℝ2×(0,∞)
is a travelling wave solution of the form ω(x,t)=W(x1−ct,x2) where W(x) is compactly supported and odd in x2. We revisit the problem of constructing solutions which are highly ε-concentrated around points (0,±q), more precisely with approximately radially symmetric, compactly supported bumps with radius ε and masses ±m. Fine asymptotic expressions are obtained, and the smooth dependence on the parameters q and ε for the solution and its propagation speed c are established. These results improve constructions through variational methods in [14] and in [5] for the case of a bounded domain.