2009/07/14 by Tuomas Hytönen, Hytonen, Tuomas, Alan McIntosh +3
Mathematics · #Advanced Harmonic Analysis Research #Spectral Theory in Mathematical Physics #Holomorphic and Operator Theory
paper · pdf · doi:10.48550/arxiv.0907.2274
We study the boundedness of the H∞ functional calculus for differential operators acting in (Lp(ℝn;ℂN)). For constant coefficients, we give simple conditions on the symbols implying such boundedness. For non-constant coefficients, we extend our recent results for the (Lp) theory of the Kato square root problem to the more general framework of Hodge-Dirac operators with variable coefficients (ΠB) as treated in (L2(ℝn;ℂN)) by Axelsson, Keith, and McIntosh. We obtain a characterization of the property that (ΠB) has a bounded (H∞) functional calculus, in terms of randomized boundedness conditions of its resolvent. This allows us to deduce stability under small perturbations of this functional calculus.