K. Leschke, K. Moriya
Manuscripta Mathematica 162(3-4) 537-558 2020年7月1日 査読有り筆頭著者最終著者責任著者
© 2019, The Author(s). The classical notion of the Darboux transformation of isothermic surfaces can be generalised to a transformation for conformal immersions. Since a minimal surface is Willmore, we can use the associated C∗-family of flat connections of the harmonic conformal Gauss map to construct such transforms, the so-called μ-Darboux transforms. We show that a μ-Darboux transform of a minimal surface is not minimal but a Willmore surface in 4-space. More precisely, we show that a μ-Darboux transform of a minimal surface f is a twistor projection of a holomorphic curve in CP3 which is canonically associated to a minimal surface fp,q in the right-associated family of f. Here we use an extension of the notion of the associated family fp,q of a minimal surface to allow quaternionic parameters. We prove that the pointwise limit of Darboux transforms of f is the associated Willmore surface of f at μ= 1. Moreover, the family of Willmore surfaces μ-Darboux transforms, μ∈ C∗, extends to a CP1 family of Willmore surfaces fμ: M→ S4 where μ∈ CP1.