Assembling a rearrangement
The author presents an algorithm which transforms a function u: [0,\(\ell]\to {\mathbb{R}}\) into its monotone decreasing rearrangement \(u^*\). His construction is motivated by a nice heuristical argument from the buoyant convection of a liquid with variable density. Mathematically this leads to a free boundary problem for a first order quasilinear equation.
scientific article; zbMATH DE number 4004805