Harmonic Spheres in the Hilbert-Schmidt Grassmannian
  We give the twistor description of harmonic maps of the Riemann sphere into the Hilbert-Schmidt Grassmannian. The study of such maps is motivated by the harmonic spheres conjecture formulated in the beginning of this paper. 
Iuliya Beloshapka, Armen G. Sergeev
math.DG math.CV