Problems / analysis
analysis / Harmonic analysis: multilinear singular integrals
The trilinear Hilbert transform conjecture at the L3 x L3 x L3 to L1 point (slopes 1, 2, 3)
Theorem 1.1: there is a finite C with ∥T(f1,f2,f3)∥L1≤C∏j∥fj∥L3 for Schwartz functions, so T extends uniquely to a bounded trilinear map L3×L3×L3→L1. The proof combines the Leng-Sah-Sawhney inverse theorem with new compression, curvature-localization and sparse counting lemmas that sum the scales without loss. It concerns only the fixed slopes 1, 2, 3 and the single exponent point (3,3,3;1): the rest of the conjectured range, other slopes, maximal or truncation-uniform versions and higher-degree multilinear Hilbert transforms are not treated, as the manuscript itself says.