​Pascal Auscher is professor of Mathematics in the Laboratoire de Mathématiques d’Orsay at the Université Paris-Saclay.  He received his PhD in 1989 at Université Paris-Dauphine under the supervision of Yves Meyer. He is a specialist in harmonic analysis and contributed to the theory of wavelets and to partial differential equations. An outstanding contribution is his participation to the proof of the Kato conjecture in any dimension, which is a starting point for boundary value problems. He has launched a systematic theory of  Hardy spaces associated to operators in relation to tent spaces, which is one core of the present monograph.  He has recently served as director of the national institute for mathematical sciences and interactions (Insmi) at the national center for scientific research (CNRS).Moritz Egert is professor of Mathematics at the Technical University of Darmstadt. He received his PhD in 2015 in Darmstadt under the supervision ofRobert Haller and was subsequently Maître de Conférences in the Laboratoire de Mathématiques d’Orsay at the Université Paris-Saclay. He is a specialist in harmonic analysis and partial differential equations. In his research, he combines methods from harmonic analysis, operator theory and geometric measure theory to study partial differential equations in non-smooth settings.