2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/112981The main aspiration of this note is to construct several different Haar-type systems in euclidean spaces of higher dimensions and prove sharp Lp bounds for the corresponding martingale transforms. In dimension one this was a result of Burkholder. The motivation for working in this direction is the search for Lp estimates of the Ahlfors-Beurling operator.41 pages, 12 figuresFunctional Analysistext