Rayleigh–Faber–Krahn inequality

The Rayleigh–Faber–Krahn inequality is a result in the field of mathematical analysis, particularly concerning eigenvalues of the Laplace operator. It provides a relationship between the eigenvalues of a bounded domain and the geometry of that domain. Specifically, the inequality states that among all domains of a given volume, the ball (or sphere, in higher dimensions) minimizes the first eigenvalue of the Laplace operator with Dirichlet boundary conditions.