Harmonicity of the Atiyah-Hitchin-Singer and Eells-Salamon almost complex structures
arXiv:1611.06496
Abstract
In this paper we describe the oriented Riemannian four-manifolds for which the Atiyah-Hitchin-Singer or Eells-Salamon almost complex structure on the twistor space of determines a harmonic map from into its twistor space.
minor changes; a detailed proof of a result announced in arXiv:1605.06804 is given