2012/11/29 by Rosén, Andreas
#Analysis of PDEs (math.AP) #FOS: Mathematics
paper · doi:10.48550/arxiv.1211.6888
We prove square function estimates in L2 for general operators of the form B1D1+D2B2, where Di are partially elliptic constant coefficient homogeneous first order self-adjoint differential operators with orthogonal ranges, and Bi are bounded accretive multiplication operators, extending earlier estimates from the Kato square root problem to a wider class of operators. The main novelty is that B1 and B2 are not assumed to be related in any way. We show how these operators appear naturally from exterior differential systems with boundary data in L2. We also prove non-tangential maximal function estimates, where our proof needs only off-diagonal decay of resolvents in L2, unlike earlier proofs which relied on interpolation and Lp estimates.