Special Session 10: Recent Developments in Regularity Theory for PDEs

The free boundary for a superlinear system
Seongmin Jeon
Hanyang University
Korea
Co-Author(s):    Daniela De Silva, Henrik Shahgholian
Abstract:
In this talk, we discuss superlinear systems that give rise to free boundaries. Such systems appear for example from the minimization of the energy functional \[ \int_{\Omega}\left(|\nabla\mathbf{u}|^2+\frac{2}{p}|\mathbf{u}|^p\right),\quad 0\lt p\lt 1, \] but solutions can be also understood in an ad hoc viscosity way. First, we prove the optimal regularity of minimizers using a variational approach. Then, we apply a linearization technique to establish the $C^{1,\alpha}$-regularity of the ``flat'' part of the free boundary via a viscosity method. Finally, for minimizing free boundaries, we extend this result to analyticity.