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arXiv · 2602.08932

Existence of expanding harmonic map flows to hemispheres

Xuanyu Li
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Abstract

We show the existence of non-trivial self-expanding harmonic map flows starting from non-energy-minimizing 0-homogeneous maps to a regular ball or a closed hemisphere. In particular, given a non-minimizing but stationary 0-homogeneous harmonic map $u_0$ to a closed hemisphere, we construct infinitely many different weak solutions to harmonic map flow starting from $u_0$, all of which satisfy the parabolic monotonicity formula. We also use a concatenation argument to solve a non-trivial smooth harmonic map flow starting from a given non-minimizing regular 0-homogeneous harmonic map, thereby yielding the non-uniqueness of harmonic map flow with monotonicity formula. This answers a question of Struwe.

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Xuanyu Li. 2026-02-09. Existence of expanding harmonic map flows to hemispheres. https://arxiv.org/abs/2602.08932

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