Yannick Sire

Johns Hopkins University

Minimizers for the thin one-phase problem

We consider the “thin one-phase” free boundary problem, associated to minimizing a weighted Dirichlet energy of the function in \(\mathbb R^{n+1}_+\) plus the area of the positivity set of that function in \(\mathbb R^n\). We establish full regularity of the free boundary for dimensions \(n \leq 2\), prove almost everywhere regularity of the free boundary in arbitrary dimension and provide content and structure estimates on the singular set of the free boundary when it exists. All of these results hold for the full range of the relevant weight. The nonlocal nature of the distributional measure associated to a minimizer necessitates arguments which are less reliant on the underlying PDE, making the techniques we develop of more general interest.