Godel-type solutions within the f(R, Q, P) gravity

In this work, we scrutinize the consistency of spacetime homogeneous Godel-type metrics within f (R, Q, P) theories of gravity for well-motivated matter sources. As it is well known, such geometries allow for causality violation. We provide general conditions to engender completely causal solutions in a manner completely different from general relativity. We take some specific models, for instance, f (R, Q, P) = R - mu(4n+2/)(aR(2) +bQ +cP)(n) ,to illustrate the general results. Notably, we also find an unusual completely causal vacuum solution in the presence of a nontrivial cosmological constant which corresponds to the case m(2) = 4 omega(2).

Automated summary

In this study, the consistency of spacetime homogeneous Godel-type metrics within f (R, Q, P) theories of gravity is examined for well-motivated matter sources. These geometries are known to allow for causality violation. General conditions are provided to generate completely causal solutions in a different manner from general relativity. Specific models, such as f (R, Q, P) = R - mu(4n+2/)(aR(2) +bQ +cP)(n), are presented to illustrate the general results. Interestingly, an unusual completely causal vacuum solution is also found in the presence of a nontrivial cosmological constant, corresponding to the case m(2) = 4 omega(2).