Instability and non-uniqueness for the 2d Euler equations in vorticity form

Abstract: In this talk, we will study the Cauchy problem for the Euler equations in vorticity form. With the initial data in L^1∩L^∞, the uniqueness of the solution is guaranteed by Yudovich's classic result. However, it is a long-standing open question if it is possible to extend the result to the L^p scale. We will disprove it by constructing a one-parameter family of solutions with the same initial data and external force.