Gradient integrability for bounded $\mathrm{BD}$-minimizers

Abstract: We establish that locally bounded relaxed minimizers of degenerate elliptic symmetric gradient functionals on $\mathrm{BD}(\Omega)$ have weak gradients in $\mathrm{L}{\mathrm{loc}}^{1}(\Omega;\mathbb{R}^{n\times n})$. This is achieved for the sharp ellipticity range that is presently known to yield $\mathrm{W}{\mathrm{loc}}^{1,1}$-regularity in the full gradient case on $\mathrm{BV}(\Omega;\mathbb{R}^{n})$. As a consequence, we also obtain the first Sobolev regularity results for minimizers of the area-type functional on $\mathrm{BD}(\Omega)$.