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On the singular set of the geodesic flow on nonpositively curved surfaces
Abstract
We prove that the singular locus of the geodesic flow on the unit tangent bundle of a nonpositively curved surface enjoys an additional regularity property: its characteristic function belongs to the geometric anisotropic Sobolev space H5/8−xH−13/16θ. In particular, this implies that if the geodesic flow is not ergodic with respect to the Liouville measure, then the zero set of the curvature must be thick in the sense that it supports a nonzero, nonnegative function in H5/8−. The proof relies on semiclassical analysis and a new radial estimate for parabolic flows.
Related
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- Singular Limits of Frame Bundles of Noncollapsing Positively Curved Manifolds
BibTeX
@misc{lefeuvre2026singular,
title = {{On the singular set of the geodesic flow on nonpositively curved surfaces}},
author = {Thibault Lefeuvre},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.16612},
eprint = {2610.16612},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.16612},
}
RIS
TY - UNPB
TI - On the singular set of the geodesic flow on nonpositively curved surfaces
AU - Thibault Lefeuvre
PY - 2026
DA - 2026/10/12
PB - arXiv
DO - 10.48550/arxiv.2610.16612
UR - https://arxiv.org/abs/2610.16612
AB - We prove that the singular locus of the geodesic flow on the unit tangent bundle of a nonpositively curved surface enjoys an additional regularity property: its characteristic function belongs to the geometric anisotropic Sobolev space H^5/8−_xH^−13/16_θ. In particular, this implies that if the geodesic flow is not ergodic with respect to the Liouville measure, then the zero set of the curvature must be thick in the sense that it supports a nonzero, nonnegative function in H^5/8−. The proof relies on semiclassical analysis and a new radial estimate for parabolic flows.
ER -