$Γ$-convergence for higher order nonlocal phase transitions
Hardy Chan, Serena Dipierro, Mattia Freguglia, Marco Inversi, Enrico Valdinoci
TL;DR
This work investigates Γ-convergence for higher-order nonlocal phase transitions by augmenting the fractional Allen–Cahn energy with the squared L2-norm of its first variation. For all $0<s<3/4$, it is shown that the first-variation term vanishes in the limit, forcing the Γ-limit of the energy pair to be a pure perimeter term: the classical perimeter when $s\ge1/2$ and the $2s$-fractional perimeter when $s<1/2$. The analysis hinges on constructing a 1D optimal-profile-based recovery sequence and a boundary expansion in Fermi coordinates that isolates the curvature contribution, which is shown to vanish in the specified range. Consequently, curvature-dependent terms do not appear in the limit in this regime, contrasting with expectations from local Willmore-type energies and highlighting intrinsic differences between local and nonlocal phase-transition limits. The results refine the understanding of nonlocal Γ-limits and guide expectations for nonlocal geometric energies in low- versus high-regularity regimes.
Abstract
For every $0 < s <3/4$, we study the asymptotic behavior of the $\varepsilon$-rescaled sum of the $s$-fractional Allen-Cahn energy and the squared $L^2$-norm of its first variation. We prove that the contribution of the first variation vanishes as $\varepsilon \to 0$. This implies the Gamma-convergence of the initial sum to either the classical perimeter or to the $2s$-fractional perimeter, depending on whether $s \ge 1/2$ or not. This contradicts the expectation of finding curvature-dependent terms in the limit, as suggested by the regime $3/4 \le s < 1$, and as known to hold in low dimensions in the local case.
