A generalized Biot–Savart law and its application to the active scalar equations

Abstract In this paper, we study a generalized Biot–Savart law for suitable velocity that possibly diverges at infinity, and then show its application to the 2D general incompressible inviscid fluids. We first prove the generalized Biot–Savart law for the active scalar equations in a discrete rotational symmetry framework, which allows the velocity grow almost linearly at infinity. Based on this, we further obtain a unique global symmetric solution to Euler equation under the Yudovich type regularity. Additionally, we investigate the local well-posedness for the Boussnesq equation, SQG equation, and especially for the IPM equation which enjoys particular symmetric property in our setting. The proof mainly relies on the Fourier model analysis and some refined estimates to the singular integral operator.