Godel-type Solutions Research Articles

Lagrangian formalism for Rastall theory of gravity and Gödel-type universe

In the Rastall gravity a non-minimal coupling between geometry and matter fields is considered. Then the usual energy-momentum tensor conservation law is not valid. Here a Lagrangian formalism is proposed to the Rastall theory of gravity. The Godel-type universe is studied in this gravitational model. Then it is studied whether this theory permits causality violation. The field equations do not exclude solutions with a breakdown of causality for a perfect fluid as matter content. In this case, an expression for the critical radius (beyond which the causality is violated) is determined. In addition, for a combination between perfect fluid and scalar field as matter content the theory accommodates causal Godel-type solution.

A study of important solutions in Chern–Simons modified gravity

In this manuscript, we have presented the compatible solutions under the framework of dynamical and non-dynamical Chern–Simons modified gravity. By taking an open choice of external field as a function of angular parameter $$\theta $$ , we obtained Godel-type solutions of non-dynamical Chern–Simons modified gravity. It is mentioned that a vacuum Godel-type solution exists in this theory. Non-static spherical symmetric solutions are also described for dynamical Chern–Simons modified gravity by considering external field as a function of radial parameter r. Later, results are similar to those of well-known Tolman–Bondi solutions found in the context of general relativity. It is observed that in case of $$\varLambda \rightarrow \kappa p_{0}$$ both parameters A(t, r) and B(t, r) turned to be undefined.

Letter: A Cylindrically Symmetric Solution in Einstein-Maxwell-Dilaton Gravity

We consider the existence of Einstein-Maxwell-dilaton plus fluid systems for the case of stationary cylindrically symmetric spacetimes. An exact inhomogeneous e-order solution is found, where the parameter e parametrizes the non-minimally coupled electromagnetic field. Some its physical attributes are investigated and a connection with the already known Godel-type solution is given. It is shown that our solution also survives in the string-inspired charged gravity framework. We find that a magnetic field has positive influence on the chronology violation unlike the dilaton influence.

A class of inhomogeneous Gödel-type models

A class of inhomogeneous Godel-type solutions of Einstein’s field equations is studied. The source of the geometries is a fluid with heat flow plus a scalar field. The thermodynamic properties of one specific solution are discussed. When the heat flux vanishes, space-time homogeneous solutions, previously found by the authors, result.