On $L^2$ Solvability of BVPs for elliptic systems
  In this article we prove solvability results for $L^2$ boundary value problems of some elliptic systems $Lu=0$ on the upper half-space $\R^{n+1}_{+}, n\ge 1$, with transversally independent coefficients. We use the first order formalism introduced by Auscher-Axelsson-McIntosh and further developed with a better understanding of the classes of solutions in the subsequent work of Auscher-Axelsson. The interesting fact is that we prove only half of the Rellich boundary inequality without knowing the other half. 
Pascal Auscher (LM-Orsay), Alan McIntosh (CMA), Mihalis Mourgoglou   (LM-Orsay)
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