Rigidity of stationary and uniformly rotating planar Euler flows in the $C^1$ Yudovich class
We prove a rigidity theorem for stationary and uniformly rotating solutions of the two-dimensional incompressible Euler equation with vorticity $ \omega_0\in C^1(\mathbb{R}^2)\cap L^1(\mathbb{R}^2) \cap L^\infty(\mathbb{R}^2). $ If the angular velocity $\Omega$ satisfies \[ \Omega\leq\frac12\inf_{\mathbb{R}^2}\omega_0...