Curved commutators in the plane

Abstract

We complete the $L^p$ boundedness theory of commutators of Hilbert transforms along monomial curves by providing the previously missing lower bounds. This optimal result now covers all monomial curves while the previous result assumed the curve to intersect adjacent quadrants of the plane. We also develop, under a qualitative $\mathrm{BMO}$ assumption of the symbol, the corresponding quantitative lower bound in the context of curves with non-vanishing torsion.

v2: 30 pages, 2 figures added, referee comments incorporated; v1: 27 pages