Revista de la
Unión Matemática Argentina
Classification of left invariant Hermitian structures on 4-dimensional non-compact rank one symmetric spaces
Srdjan Vukmirović, Marijana Babić, and Andrijana Dekić
Volume 60, no. 2 (2019), pp. 343–358    

https://doi.org/10.33044/revuma.v60n2a04

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Abstract

The only 4-dimensional non-compact rank one symmetric spaces are $\mathbb{C}H^2$ and $\mathbb{R}H^4$. By the classical results of Heintze, one can model these spaces by real solvable Lie groups with left invariant metrics. In this paper we classify all possible left invariant Hermitian structures on these Lie groups, i.e., left invariant Riemannian metrics and the corresponding Hermitian complex structures. We show that each metric from the classification on $\mathbb{C}H^2$ admits at least four Hermitian complex structures. One class of metrics on $\mathbb{C}H^2$ and all the metrics on $\mathbb{R}H^4$ admit 2-spheres of Hermitian complex structures. The standard metric of $\mathbb{C}H^2$ is the only Einstein metric from the classification, and also the only metric that admits Kähler structure, while on $\mathbb{R}H^4$ all the metrics are Einstein. Finally, we examine the geometry of these Lie groups: curvature properties, self-duality, and holonomy.