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Guendelman, E. I., Olmo, G. J., Rubiera-Garcia, D., & Vasihoun, M. (2013). Nonsingular electrovacuum solutions with dynamically generated cosmological constant. Phys. Lett. B, 726(4-5), 870–875.
Abstract: We consider static spherically symmetric configurations in a Palatini extension of General Relativity including R-2 and Ricci-squared terms, which is known to replace the central singularity by a wormhole in the electrovacuum case. We modify the matter sector of the theory by adding to the usual Maxwell term a nonlinear electromagnetic extension which is known to implement a confinement mechanism in flat space. One feature of the resulting theory is that the nonlinear electric field leads to a dynamically generated cosmological constant. We show that with this matter source the solutions of the model are asymptotically de Sitter and possess a wormhole topology. We discuss in some detail the conditions that guarantee the absence of singularities and of traversable wormholes.
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Olmo, G. J., & Pinto, M. A. S. (2025). On Energy-Momentum Conservation in Non-Minimal Geometry-Matter Coupling Theories. Universe, 11(12), 386–10pp.
Abstract: In this work, we discuss the conditions that allow the establishment of an equivalence between f(R,T)=R+lambda h(T) gravity models and General Relativity (GR) coupled to a modified matter sector. We do so by considering a D-dimensional spacetime and the matter sector described by nonlinear electrodynamics and/or a scalar field. We find that, for this particular family of models, the action and field equations can indeed be written in terms of a modified matter source within GR. However, when several matter sources are combined, this interpretation is no longer possible if h(T) is a nonlinear function, due to the emergence of crossed terms that mix together the scalar and vector sectors.
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