Permutation symmetric solutions of the incompressible Euler equation

In this paper, we study permutation symmetric solutions of the incompressible Euler equation. We show that the dynamics of these solutions can be reduced to an evolution equation on a single vorticity component ω₁, and we characterize the relevant constraint space for this vorticity component under permutation symmetry. We also give single vorticity component versions of the energy equality, Beale-Kato-Majda criterion, and local wellposedness theory that are specific to the permutation symmetric case. This paper is significantly motivated by recent work of the author [11], which proved finite-time blowup for solutions of a Fourier-restricted Euler model equation, where the Helmholtz projection is replaced by a projection onto a more restrictive constraint space. The blowup solutions for this model equation are odd, permutation symmetric, and mirror symmetric about the plane x₁+x₂+x₃=0. Using the blowup solution introduced by Elgindi in [5], we are able to show that there are C1,α solutions of the full Euler equation that are odd, permutation symmetric, and mirror symmetric about the plane x₁+x₂+x₃=0, that blowup in finite-time.