2026/02/28 by Xingyu Wang
Mathematics · #math.AP
Comments are welcome
arxiv created 2026/08/01 · arxiv updated 2026/08/04
We study the sharp-interface limit of a matrix-valued Allen--Cahn equation with the Saint Venant--Kirchhoff potential F(A)=\frac14‖AA^\top-I‖2 . The zero set of this potential is the orthogonal group \mathbbOn=\mathbbOn+∪\mathbbOn-, and the corresponding limiting problem combines mean-curvature motion of the interface with harmonic-map heat flow in the two bulk phases. The proof combines a modulated-energy argument with compactness estimates obtained from two skew-symmetric commutator formulations of the equation. The method avoids the spectral analysis of linearized operators around quasi-minimal connecting orbits and the construction of high-order matched asymptotic expansions. In particular, the limiting maps satisfy the minimal-pair condition on the moving interface and the weak transmission identities which, for smooth limits, are equivalent to the Neumann-type jump condition of the sharp-interface system.