Non-uniformly elliptic variational problems on BV
Lisa Beck, Franz Gmeineder, Mathias Schäffner
TL;DR
This work addresses regularity for relaxed minimizers of convex functionals with linear growth on BV, a regime that sits at the endpoint between standard superlinear $(p,q)$-growth and pure linear growth. By employing Lebesgue–Serrin–Marcellini relaxation and a carefully designed Ekeland-vanishing viscosity scheme, the authors derive universal $ ext{W}^{1,1}$-regularity and higher gradient integrability under a non-uniform ellipticity condition parameterized by $(oldsymbol{ extmu},q)$, with $q+oldsymbol{ extmu}<2+rac{2}{n-1}$ and dimension-dependent lower bounds on $oldsymbol{ extmu}$. In two dimensions, a stronger set of assumptions yields local $C^{1,oldsymbol{eta}}$-regularity for relaxed minimizers. The results bridge the gap between the linear-growth endpoint and the superlinear regime, provide a sharp gradient-integrability framework, and include a dimension reduction for the singular set, all while avoiding integral representations of the relaxed functional and relying on BV-based analysis and measure-theoretic techniques. The methods have potential implications for endpoint growth problems such as $L ext{log}L$-type growth and other non-uniformly elliptic BV-variational problems.
Abstract
We establish $\mathrm{W}^{1,1}$-regularity and higher gradient integrability for relaxed minimizers of convex integral functionals on $\mathrm{BV}$. Unlike classical examples such as the minimal surface integrand, we only require linear growth from below but not necessarily from above. This typically comes with a non-uniformly degenerate elliptic behaviour, for which our results extend the presently available bounds from the superlinear growth case in a sharp way.
