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Continuation of the zero set for discretely self-similar solutions to the Euler equations

We are concerned on the study of the unique continuation type property for the 3D incompressible Euler equations in the self-similar type form. Discretely self-similar solution is a generalized notion of the self-similar solution, which is equivalent to a time periodic solution of the time dependent self-similar Euler equations. We prove the unique continuation type theorem for the discretely self-similar solutions to the Euler equations in $\Bbb R^3$. More specifically, we suppose there exists an open set $G\subset \Bbb R^3$ containing the origin such that the velocity field $V\in C_s^1C^{2}_y (\Bbb R^{3+1})$ vanishes on $G\times (0, S_0)$, where $S_0 > 0$ is the temporal period for $V(y,s)$. Then, we show $V(y,s)=0$ for all $(y,s)\in \Bbb R^{3+1}$. Similar property also holds for the inviscid magnetohydrodynamic system