@article{10.2307/41582748,
 ISSN = {00361429},
 URL = {http://www.jstor.org/stable/41582748},
 abstract = {The optimal design task of this paper seeks the distribution of two materials of prescribed amounts for maximal torsion stiffness of an infinite bar of a given cross section. This example of relaxation in topology optimization leads to a degenerate convex minimization problem $E(v): = \int_\Omega {{\varphi _0}} (|\nabla v|)dx - \int_\Omega {fvdx} $ for $v \in V: = H_0^1\left( \Omega \right)$ with possibly multiple primal solutions u, but with unique stress $\sigma : = \varphi _0^1\left( {|\nabla u|} \right)$ sign ∇u. The mixed finite element method is motivated by the smoothness of the stress variable $\sigma \in H_{loc}^1\left( {\Omega ;{\mathbb{R}^2}} \right)$ , while the primal variables are uncontrollable and possibly nonunique. The corresponding nonlinear mixed finite element method is introduced, analyzed, and implemented. The striking result of this paper is a sharp a posteriori error estimation in the dual formulation, while the a posteriori error analysis in the primal problem suffers from the reliability-efficiency gap. An empirical comparison of that primal formulation with the new mixed discretization schemes is intended for uniform and adaptive mesh refinements.},
 author = {CARSTEN CARSTENSEN and DAVID GÜNTHER and HELLA RABUS},
 journal = {SIAM Journal on Numerical Analysis},
 number = {2},
 pages = {522--543},
 publisher = {Society for Industrial and Applied Mathematics},
 title = {MIXED FINITE ELEMENT METHOD FOR A DEGENERATE CONVEX VARIATIONAL PROBLEM FROM TOPOLOGY OPTIMIZATION},
 volume = {50},
 year = {2012}
}