Limiting behavior of minimizing $p$-harmonic maps in 3d as $p$ goes to $2$ with finite fundamental group
Bohdan Bulanyi, Jean Van Schaftingen, Benoît Van Vaerenbergh
TL;DR
The paper analyzes the asymptotics of minimizing $p$-harmonic maps from a bounded 3D domain into a compact manifold $\\mathcal N$ with finite $\\pi_1(\\mathcal N)$ as $p\\nearrow 2$. It proves that a subsequence converges to a locally harmonic map $u_*$ on $\\Omega\\setminus S_*$, where $S_*$ is a finite-length singular set that, inside the domain, is a finite union of straight segments minimizing a homotopical mass. The limiting stress-energy measures converge to a stationary 1-dimensional rectifiable varifold $V_*$ supported on $S_*$, with densities drawn from a finite set of singular energies associated to boundary loops. Under extra regularity and boundary convexity, a boundary repulsion phenomenon ties $S_*$ to the boundary data, ensuring $S_*\\cap\\partial\\Omega$ matches prescribed singularities $S(g)$. Together, these results provide a detailed structure for energy concentration, singular set geometry, and boundary interactions in the 3D, non-simply connected target setting as $p\to 2$.
Abstract
We study the limiting behavior of minimizing $p$-harmonic maps from a bounded Lipschitz domain $Ω\subset \mathbb{R}^{3}$ to a compact connected Riemannian manifold without boundary and with finite fundamental group as $p \nearrow 2$. We prove that there exists a closed set $S_{*}$ of finite length such that minimizing $p$-harmonic maps converge to a locally minimizing harmonic map in $Ω\setminus S_{*}$. We prove that locally inside $Ω$ the singular set $S_{*}$ is a finite union of straight line segments, and it minimizes the mass in the appropriate class of admissible chains. Furthermore, we establish local and global estimates for the limiting singular harmonic map. Under additional assumptions, we prove that globally in $\overlineΩ$ the set $S_{*}$ is a finite union of straight line segments, and it minimizes the mass in the appropriate class of admissible chains, which is defined by a given boundary datum and $Ω$.
