Advances in Mathematics 224 (2010) 2511–2530 www.elsevier.com/locate/aim The Codazzi equation for surfaces ✩ Juan A. Aledo a,JoséM.Espinarb, José A. Gálvez c,∗ a Departamento de Matemáticas, Universidad de Castilla-La Mancha, EPSA, 02071 Albacete, Spain b Institut de Mathématiques, Université Paris VII, 175 Rue du Chevaleret, 75013 Paris, France c Departamento de Geometría y Topología, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain Received 20 February 2009; accepted 9 February 2010 Available online 1 March 2010 Communicated by Gang Tian Abstract In this paper we study the classical Codazzi equation in space forms from an abstract point of view, and use it as an analytic tool to derive global results for surfaces in different ambient spaces. In particular, we study the existence of holomorphic quadratic differentials, the uniqueness of immersed spheres in geometric problems, height estimates, and the geometry and uniqueness of complete or properly embedded Weingarten surfaces. © 2010 Elsevier Inc. All rights reserved. Keywords: Codazzi equation; Holomorphic quadratic differentials; Height estimates; Uniqueness and completeness of surfaces 1. Introduction The Codazzi equation for an immersed surface Σ in Euclidean 3-space R3 yields ∇XSY −∇Y SX − S[X, Y ]=0,X,Y∈ X(Σ). (1) ✩ The first author is partially supported by Junta de Comunidades de Castilla-La Mancha, Grant No. PCI-08-0023. The second and third authors are partially supported by Grupo de Excelencia P06-FQM-01642 Junta de Andalucía. The authors are partially supported by MCYT-FEDER, Grant No. MTM2007-65249. * Corresponding author. E-mail addresses:
[email protected] (J.A.