Radó's theorem (harmonic functions)

In mathematics, Radó's theorem is a result about harmonic functions, named after Tibor Radó.

Informally, it says that any "nice looking" shape without holes can be smoothly deformed into a disk.

Suppose Ω is an open, connected and convex subset of the Euclidean space R2 with smooth boundary ∂Ω and suppose that D is the unit disk.

Then, given any homeomorphism μ : ∂D → ∂Ω, there exists a unique harmonic function u : D → Ω such that u = μ on ∂D and u is a diffeomorphism.

This article incorporates material from Rado's theorem on PlanetMath, which is licensed under the Creative Commons Attribution/Share-Alike License.