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Continuity of infinitely degenerate weak solutions...
Journal article

Continuity of infinitely degenerate weak solutions via the trace method

Abstract

In 1971 Fediĭ proved in [3] the remarkable theorem that the linear second order partial differential operator L f u ( x , y ) ≡ { ∂ ∂ x 2 + f ( x ) 2 ∂ ∂ y 2 } u ( x , y ) is hypoelliptic provided that f ∈ C ∞ ( R ) , f ( 0 ) = 0 and f is positive on ( − ∞ , 0 ) ∪ ( 0 , ∞ ) . Variants of this result, with hypoellipticity replaced by continuity of weak solutions, were recently given by the authors, together with Cristian Rios and Ruipeng Shen, in [16] to infinitely degenerate elliptic divergence form equations ∇ tr A ( x , u ) ∇ u = ϕ ( x ) , x ∈ Ω ⊂ R n , where the nonnegative matrix A ( x , u ) has bounded measurable coefficients with trace roughly 1 and determinant comparable to f 2 , and where F = ln ⁡ 1 f is essentially doubling. However, in the plane, these variants assumed additional geometric constraints on f, such as f ( r ) ≥ e − r − σ for some 0 < σ < 1 , something not required in Fediĭ's theorem. In this paper we in particular remove these additional geometric constraints in the plane for homogeneous equations, and only assume that f is positive away from the origin.

Authors

Korobenko L; Sawyer E

Journal

Journal of Functional Analysis, Vol. 281, No. 9,

Publisher

Elsevier

Publication Date

November 1, 2021

DOI

10.1016/j.jfa.2021.109170

ISSN

0022-1236

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