A gap theorem for $\alpha$-harmonic maps between two-spheres

Abstract

In this paper we consider approximations introduced by Sacks-Uhlenbeck of the harmonic energy for maps from $S^2$ into $S^2$. We continue the analysis in [6] about limits of $\alpha$-harmonic maps with uniformly bounded energy. Using a recent energy identity in [7], we obtain an optimal gap theorem for the $\alpha$-harmonic maps of degree $-1, 0$ or $1$.Comment: Final version, to appear in Anal. PD