A Multidimensional Birkhoff Theorem for some C0 Lagrangians
Abstract
We prove a multidimensional Birkhoff theorem for a new class of "C0 Lagrangian subsets" in cotangent bundles, obtained as Hausdorff limits of compact exact Lagrangian submanifolds with control on their Liouville primitives. If the successive images of such a subset L under the flow of a Tonelli Hamiltonian admit convergent subsequences in both positive and negative time, then L and all its images are Lipschitz graphs over the base. This extends Birkhoff's celebrated theorem for twist maps of the annulus and its known higher-dimensional generalizations, and provides a first version of such results for merely continuous objects. The proof combines Floer-theoretic graph selectors, variational solutions of the Hamilton-Jacobi equation, and weak KAM theory. We also investigate the rigidity and uniqueness of limiting primitives for this new class of singular Lagrangian subsets, which may be of independent interest in C0 symplectic topology.
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BibTeX
@misc{charfi2026multidimensional,
title = {{A Multidimensional Birkhoff Theorem for some $C^0$ Lagrangians}},
author = {Skander Charfi and Ibrahim Trifa},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.28373},
eprint = {2609.28373},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.28373},
}
RIS
TY - UNPB
TI - A Multidimensional Birkhoff Theorem for some C^0 Lagrangians
AU - Skander Charfi
AU - Ibrahim Trifa
PY - 2026
DA - 2026/10/16
PB - arXiv
DO - 10.48550/arxiv.2609.28373
UR - https://arxiv.org/abs/2609.28373
AB - We prove a multidimensional Birkhoff theorem for a new class of "C^0 Lagrangian subsets" in cotangent bundles, obtained as Hausdorff limits of compact exact Lagrangian submanifolds with control on their Liouville primitives. If the successive images of such a subset L under the flow of a Tonelli Hamiltonian admit convergent subsequences in both positive and negative time, then L and all its images are Lipschitz graphs over the base. This extends Birkhoff's celebrated theorem for twist maps of the annulus and its known higher-dimensional generalizations, and provides a first version of such results for merely continuous objects. The proof combines Floer-theoretic graph selectors, variational solutions of the Hamilton-Jacobi equation, and weak KAM theory. We also investigate the rigidity and uniqueness of limiting primitives for this new class of singular Lagrangian subsets, which may be of independent interest in C^0 symplectic topology.
ER -