Type N Spacetimes as Solutions of Extended New Massive Gravity

Understand

We study algebraic type N spacetimes in the extended new massive gravity (NMG), considering both the Born-Infeld model (BI-NMG) and the model of NMG with any finite order curvature corrections.

• We show that for these spacetimes, the field equations of BI-NMG take the form of the massive (tensorial) Klein-Gordon type equation, just as it happens for ordinary NMG.
• This fact enables us to obtain the type N solution to BI-NMG, utilizing the general type N solution of NMG, earlier found in our work.
• We also obtain type N solutions to NMG with all finite order curvature corrections and show that, in contrast to BI-NMG, this model admits the critical point solutions, which are counterparts of "logarithmic" AdS pp-waves solutions of NMG.