Minimizing under relaxed symmetry constraints: Triple and $N$-junctions

TL;DR

This paper proves the existence of N-junction solutions to the vector Allen-Cahn equation with a symmetric potential, using variational methods and energy bounds, extending understanding of phase transitions with relaxed symmetry constraints.

Contribution

It introduces a variational approach to establish N-junction solutions for potentials with N nondegenerate zeros and rotational symmetry, relaxing previous symmetry constraints.

Findings

Existence of N-junction solutions proven.

New pointwise estimates for vector minimizers developed.

Energy bounds are established for solutions.

Abstract

We consider a nonnegative potential $W:\mathbb{R}^2\rightarrow\mathbb{R}$ invariant under the action of the rotation group $C_N$ of the regular polygon with $N$ sides, $N\geq 3$. We assume that $W$ has $N$ nondegenerate zeros and prove the existence of a $N$-junction solution to the vector Allen-Cahn equation. The proof is variational and is based on sharp lower and upper bounds for the energy and on a new pointwise estimate for vector minimizers.