Type N spacetimes as solutions of extended new massive gravity

Abstract

We study algebraic type N spacetimes in the extended new massive gravity\n(NMG), considering both the Born-Infeld model (BI-NMG) and the model of NMG\nwith any finite order curvature corrections. We show that for these spacetimes,\nthe field equations of BI-NMG take the form of the massive (tensorial)\nKlein-Gordon type equation, just as it happens for ordinary NMG. This fact\nenables us to obtain the type N solution to BI-NMG, utilizing the general type\nN solution of NMG, earlier found in our work. We also obtain type N solutions\nto NMG with all finite order curvature corrections and show that, in contrast\nto BI-NMG, this model admits the critical point solutions, which are\ncounterparts of "logarithmic" AdS pp-waves solutions of NMG.\n