Fixed geodesics of involutions on $3$-spheres
Abstract
Let an isometric involution act on a smooth Riemannian $3$-sphere with sectional curvature at least one. We prove that every one-dimensional connected component of its fixed-point set has length at most 2π, and that the bound is sharp. The proof realizes the fixed circle as the link of a complete totally geodesic surface in a positively curved expanding Ricci soliton and applies Bishop--Gromov comparison to its area growth. The analytic input is an equivariant version of Deruelle's smoothing of positively curved cones. We use Gianniotis--Schulze's equivariant local deformation and explain a marked compactness argument for arbitrary finite isotropy. In particular, the end chart retains the specified group action, rather than only an unspecified conjugate.
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BibTeX
@misc{shen2026fixed,
title = {{Fixed geodesics of involutions on $3$-spheres}},
author = {Bin Shen and Hui Zhang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.29796},
eprint = {2610.29796},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.29796},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Fixed geodesics of involutions on $3$-spheres
AU - Bin Shen
AU - Hui Zhang
PY - 2026
DA - 2026/10/21
PB - arXiv
DO - 10.48550/arxiv.2610.29796
UR - https://arxiv.org/abs/2610.29796
AB - Let an isometric involution act on a smooth Riemannian $3$-sphere with sectional curvature at least one. We prove that every one-dimensional connected component of its fixed-point set has length at most 2π, and that the bound is sharp. The proof realizes the fixed circle as the link of a complete totally geodesic surface in a positively curved expanding Ricci soliton and applies Bishop--Gromov comparison to its area growth. The analytic input is an equivariant version of Deruelle's smoothing of positively curved cones. We use Gianniotis--Schulze's equivariant local deformation and explain a marked compactness argument for arbitrary finite isotropy. In particular, the end chart retains the specified group action, rather than only an unspecified conjugate.
ER -