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arXiv · 2212.07977

A trajectorial interpretation of Moser's proof of the Harnack inequality

Lukas Niebel·Rico Zacher
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Abstract

In 1971 Moser published a simplified version of his proof of the parabolic Harnack inequality. The core new ingredient is a fundamental lemma due to Bombieri and Giusti, which combines an $L^p-L^\infty$-estimate with a weak $L^1$-estimate for the logarithm of supersolutions. In this note, we give a novel proof of this weak $L^1$-estimate. The presented argument uses parabolic trajectories and does not use any Poincar\'e inequality. Moreover, the proposed argument gives a geometric interpretation of Moser's result and could allow transferring Moser's method to other equations.

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Lukas Niebel, Rico Zacher. 2022-12-15. A trajectorial interpretation of Moser's proof of the Harnack inequality. https://doi.org/10.2422/2036-2145.202302_004

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