J. L. Rosa, J. P. S. Lemos, F. S. N. Lobo
Wormhole solutions in a generalized hybrid metric-Palatini matter theory, given by a gravitational Lagrangian density f (R, ℛ), where R is the metric Ricci scalar, and ℛ is a Palatini scalar curvature defined in terms of an independent connection, and a matter Lagrangian, are found. The solutions are worked out in the scalar-tensor representation of the theory, where the Palatini field is traded for two scalars, ϕ and ψ, and the gravitational term R is maintained. The main interest in the solutions found is that the matter field obeys the null energy conditions everywhere, including the throat and up to infinity, so that there is no need for exotic matter. The wormhole geometry with its flaring out at the throat is supported by the higher-order curvature terms, or equivalently, by the two fundamental scalar fields, which either way can be interpreted as a gravitational fluid. Thus, in this theory, in building a wormhole, it is possible to exchange the exoticity of matter by the exoticity of the gravitational sector.
Wormholes; modified gravity; hybrid metric-Palatini gravity
The Fifteenth Marcel Grossmann Meeting
Elia S Battistelli, Robert T Jantzen, Remo Ruffini
World Scientific Publishing Co. Pte. Ltd., Page 588