Supercritical equivariant biharmonic maps from ${\mathbf{R}}^5$ into $S^5$

Abstract

We study supercritical $O(d)$-equivariant biharmonic maps with a focus on $d=5$, where $d$ is the dimension of the domain. We give a characterisation of non-trivial equivariant biharmonic maps from ${\mathbf{R}}^5$ into $S^5$ as heteroclinic orbits of an associated dynamical system. Moreover, we prove the existence of such non-trivial equivariant biharmonic maps. Finally, in stark contrast to the harmonic map analogue, we show the existence of an equivariant biharmonic map from $B^5(0,1)$ into $S^5$ that winds around $S^5$ infinitely many times.