Exact solutions of Klein–Gordon equations in external electromagnetic fields on 3D de Sitter background.

We study symmetry properties and the possibility of exact integration of Klein–Gordon equations in external electromagnetic fields on 3D de Sitter background dS3. We present an algorithm for constructing the first-order symmetry algebra and describe its structure in terms of Lie algebra extensions. Based on the well-known classification of the subalgebras of the algebra s o (1 , 3) , we classify all electromagnetic fields on dS3 for which the corresponding Klein–Gordon equations admit first-order symmetry algebras. Then, we select the integrable cases, and for each of them, we construct exact solutions using the noncommutative integration method developed by Shapovalov and Shirokov [Theor. Math. Phys. 104, 921–934 (1995)]. We also propose an original algebraic method for constructing the special local coordinates on de Sitter space dS3, in which basis vector fields for subalgebras of the Lie algebra s o (1 , 3) have the simplest form. [ABSTRACT FROM AUTHOR]