Uniqueness of constant scalar curvature Kähler metrics with cone singularities. I: reductivity

The aim of this paper is to investigate uniqueness of conic constant scalar curvature Kähler (cscK) metrics, when the cone angle is less than π\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pi $$\end{document}. We introduce a new Hölder space called C4,α,β\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathcal {C}}^{4,\alpha ,\beta }$$\end{document} to study the regularities of this fourth order elliptic equation, and prove that any C2,α,β\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathcal {C}}^{2,\alpha ,\beta }$$\end{document} conic cscK metric is indeed of class C4,α,β\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathcal {C}}^{4,\alpha ,\beta }$$\end{document}. Finally, the reductivity is established by a careful study of the conic Lichnerowicz operator.