On purely real surfaces in Kaehler surfaces

Authors: BANG-YEN CHEN

Abstract: An immersion \phi colon M to \tilde M^2 of a surface M into a Kaehler surface is called purely real if the complex structure J on \tilde M^2 carries the tangent bundle of M into a transversal bundle. In the first part of this article, we prove that the equation of Ricci is a consequence of the equations of Gauss and Codazzi for purely real surfaces in any Kaehler surface. In the second part, we obtain a necessary condition for a purely real surface in a complex space form to be minimal. Several applications of this condition are provided. In the last part, we establish a general optimal inequality for purely real surfaces in complex space forms. We also obtain three classification theorems for purely real surfaces in C^2 which satisfy the equality case of the inequality.

Keywords: Purely real surfaces; integrability condition; equation of Ricci; equation of Gauss-Codazzi; Kaehler surface; Wirtinger angle; optimal inequality.

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