Symmetry Breaking and Moduli for Ancient Yamabe Flows on the Sphere
Abstract
For every n≥3, we construct compact Type II ancient Yamabe flows in the round conformal class of the unit n-sphere Ssn. After stereographic projection and rescaling of time and conformal factor, the solutions are asymptotic backward in time to finite superpositions of Aubin--Talenti bubbles with mutually comparable scales. For integers h≥1 and k≥2, the limiting centers form h coaxial regular k-gons; when h≥2, their distinct layer heights may be prescribed arbitrarily in the interval (−1,1). If hk≥3, the resulting flows are not geometrically equivalent to any rotationally symmetric ancient flow. For each flow, there is a fixed point of Ssn at which the Ricci tensor has both positive and negative eigenvalues on every time slice. The corresponding volume-normalized Yamabe flows are also ancient. After rescaling each time slice to a fixed volume, the metrics converge to a wedge of hk isometric round n-spheres in the Gromov--Hausdorff topology, as time tends to −∞. For fixed h,k≥2, the concentration configurations admit an explicit (h−1)-parameter description up to Möbius transformations. Consequently, the construction yields geometrically inequivalent flows indexed by a nonempty open subset of Rh−1, all with the same fixed-volume backward Gromov--Hausdorff limit. The proof uses inner--outer gluing for the quasilinear parabolic equation in n-dimensional space that exhibits Kelvin symmetry. Weighted Euclidean and spherical Hölder estimates control the nonlinear terms and, together with parabolic regularity, yield smooth extension of the conformal metrics across the north pole of Ssn.
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BibTeX
@misc{chen2026symmetry,
title = {{Symmetry Breaking and Moduli for Ancient Yamabe Flows on the Sphere}},
author = {Haixia Chen and Seunghyeok Kim and Monica Musso},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2606.22355},
eprint = {2606.22355},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.22355},
}
RIS
TY - UNPB
TI - Symmetry Breaking and Moduli for Ancient Yamabe Flows on the Sphere
AU - Haixia Chen
AU - Seunghyeok Kim
AU - Monica Musso
PY - 2026
DA - 2026/10/23
PB - arXiv
DO - 10.48550/arxiv.2606.22355
UR - https://arxiv.org/abs/2606.22355
AB - For every n≥3, we construct compact Type II ancient Yamabe flows in the round conformal class of the unit n-sphere Ss^n. After stereographic projection and rescaling of time and conformal factor, the solutions are asymptotic backward in time to finite superpositions of Aubin--Talenti bubbles with mutually comparable scales. For integers h≥1 and k≥2, the limiting centers form h coaxial regular k-gons; when h≥2, their distinct layer heights may be prescribed arbitrarily in the interval (−1,1). If hk≥3, the resulting flows are not geometrically equivalent to any rotationally symmetric ancient flow. For each flow, there is a fixed point of Ss^n at which the Ricci tensor has both positive and negative eigenvalues on every time slice. The corresponding volume-normalized Yamabe flows are also ancient. After rescaling each time slice to a fixed volume, the metrics converge to a wedge of hk isometric round n-spheres in the Gromov--Hausdorff topology, as time tends to −∞. For fixed h,k≥2, the concentration configurations admit an explicit (h−1)-parameter description up to Möbius transformations. Consequently, the construction yields geometrically inequivalent flows indexed by a nonempty open subset of R^h−1, all with the same fixed-volume backward Gromov--Hausdorff limit. The proof uses inner--outer gluing for the quasilinear parabolic equation in n-dimensional space that exhibits Kelvin symmetry. Weighted Euclidean and spherical Hölder estimates control the nonlinear terms and, together with parabolic regularity, yield smooth extension of the conformal metrics across the north pole of Ss^n.
ER -