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The Kato square root problem for weighted parabolic operators

Alireza Ataei, Moritz Egert and Kaj Nyström

Vol. 18 (2025), No. 1, 141–169
Abstract

We give a simplified and direct proof of the Kato square root estimate for parabolic operators with elliptic part in divergence form and coefficients possibly depending on space and time in a merely measurable way. The argument relies on the nowadays classical reduction to a quadratic estimate and a Carleson-type inequality. The precise organization of the estimates is different from earlier works. In particular, we succeed in separating space and time variables almost completely despite the nonautonomous character of the operator. Hence, we can allow for degenerate ellipticity dictated by a spatial A2-weight, which has not been treated before in this context.

Keywords
Kato square root problem, second-order parabolic operators, Muckenhoupt weights, square function estimates, fractional derivatives
Mathematical Subject Classification
Primary: 35K10, 42B25, 42B37
Secondary: 26A33, 47B44
Milestones
Received: 22 September 2022
Revised: 30 August 2023
Accepted: 19 September 2023
Published: 15 December 2024
Authors
Alireza Ataei
Department of Mathematics
Uppsala University
Uppsala
Sweden
Moritz Egert
Fachbereich Mathematik
TU Darmstadt
Darmstadt
Germany
Kaj Nyström
Department of Mathematics
Uppsala University
Uppsala
Sweden

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