Black branes in four-dimensional conformal equivalent theories

The physical properties of static analytic solutions which describe black brane geometries are discussed. In particular we study the similarities and differences of analytic black brane/string solutions in the Einstein and Jordan frames. The comparison is made between vacuum power law $f(R)$ gravity solutions and their conformal equivalents in the Einstein frame. In our analysis we examine how the geometrical and physical properties of these analytic axisymmetric solutions - such as singularities, the temperature and the entropy - are affected as we pass from one frame to the other.Comment: 12 pages, no figure

(Compactified) black branes in four dimensional f(R)-gravity

A new family of analytical solutions in a four dimensional static spacetime is presented for $f\left( R\right)$-gravity. In contrast to General Relativity, we find that a non trivial black string/ring solution is supported in vacuum power law $f\left( R\right)$-gravity for appropriate values of the parameters characterizing the model and when axisymmetry is introduced in the line element. For the aforementioned solution, we perform a brief investigation over its basic thermodynamic quantities.Comment: 13 pages, 3 figures, title changed, minor corrections, new references, accepted version for publication at Physics Letter