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A simple proof of the 1-dimensional flat chain conjecture

  • Andrea Marchese and Andrea Merlo ORCID logo EMAIL logo
Published/Copyright: August 29, 2025

Abstract

We provide a new proof of the fact that metric 1-currents with compact support in the Euclidean space correspond to Federer–Fleming flat chains; that is, the 1-dimensional case of the so-called flat chain conjecture. While previous proofs rely on the delicate task of constructing Lipschitz functions with small L -norm but large derivative along certain directions at all points of a given Lebesgue null set (the so-called width functions), our approach is based primarily on Poincaré’s lemma. This perspective allows us to identify a regularity question concerning the solvability of the equation d ω = π for differential k-forms, a question that is closely related to the general validity of the flat chain conjecture in higher dimensions.

MSC 2020: 49Q15; 49Q20

Communicated by Yoshihiro Tonegawa


Award Identifier / Grant number: PRIN “Geometric Measure Theory: Structure of Singu”

Award Identifier / Grant number: Marie Skłodowska-Curie grant agreement no. 1010653

Funding statement: Andrea Marchese is partially supported by the PRIN project 2022PJ9EFL “Geometric Measure Theory: Structure of Singular Measures, Regularity Theory and Applications in the Calculus of Variations” and by GNAMPA-INdAM. Andrea Merlo is supported by the European Union’s Horizon Europe research and innovation programme under the Marie Skłodowska-Curie grant agreement no 101065346.

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Received: 2025-03-06
Accepted: 2025-07-23
Published Online: 2025-08-29

© 2025 Walter de Gruyter GmbH, Berlin/Boston

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