The ball still wins: a journey into p-Laplacian eigenvalues as p→+∞

The optimization of eigenvalues of elliptic operators with respect to the geometry of the domain is a central topic in spectral geometry and shape optimization. In many classical settings, and in particular among domains with fixed volume, the ball arises as the optimal shape, either minimizing or maximizing the first eigenvalue. In this talk, we focus on the first eigenvalue of the p-Laplacian under several types of boundary conditions and we investigate its behavior from both an optimization and an asymptotic point of view. For finite values of p, we discuss the validity of extremal properties, with special attention to Robin boundary conditions. We then analyze the behavior as p→+∞, showing that, in the case of a negative Robin parameter, the limit of the eigenvalues becomes independent of the geometry of the domain. Despite this apparent loss of geometric sensitivity, the ball continues to play an optimal role, answering in this particular case a long-standing conjecture. - Seminario nell'ambito del ciclo di seminari ASK -