2017/10/02 by Kriventsov, Dennis, Lin, Fanghua · 2 citations
#35R35 #49N60 #49R05 #Analysis of PDEs (math.AP) #FOS: Mathematics
paper · doi:10.48550/arxiv.1710.00451
We consider minimizers of F(λ1(Ω),…,λN(Ω)) + |Ω|, where F is a function nondecreasing in each parameter, and λk(Ω) is the k-th Dirichlet eigenvalue of Ω. This includes, in particular, functions F which depend on just some of the first N eigenvalues, such as the often studied F=λN. The existence of a minimizer, which is also a bounded set of finite perimeter, was shown recently. Here we show that the reduced boundary of the minimizers Ω is made up of smooth graphs, and examine the difficulties in classifying the singular points. Our approach is based on an approximation ("vanishing viscosity") argument, which--counterintuitively--allows us to recover an Euler-Lagrange equation for the minimizers which is not otherwise available.