Abstract
We study a class of exact solutions of Einstein's equations described by the Plebański-Demiański metric with both repeated PNDs nonexpanding. Such spacetimes of type D contain 7 free parameters, including electric/magnetic charges and a cosmological constant.
To investigate their specific geometrical and physical properties we first carefully analyze the corresponding conformally flat backgrounds, in particular de Sitter and anti-de Sitter universe in the Plebański-Demiański coordinates (new parametrizations of the embedding hyperboloid, global conformal diagrams, transformations to well-known forms, etc.). Then we study the more general case of B-metrics with a cosmological constant, extending the Gott (1974) interpretation of BI-metric as a part of spacetime with a tachyon singularity, possibly with an electromagnetic field for nonzero charges, and also a nonsingular generalization of these metrics.