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RESEARCH PRODUCT

Geons in Palatini Theories of Gravity

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An explicit implementation of geons in the context of gravitational theories extending general relativity is discussed in detail. Such extensions are formulated in the Palatini approach, where metric and affine connection are regarded as independent entities. This formulation is inspired on the macroscopic description of the physics of crystalline structures with defects in the context of solid-state physics, whose study can provide valuable lessons for going beyond GR. We discuss several theories for the gravitational field including additional contributions of the Ricci tensor in four and higher dimensions. As opposed to the standard metric approach, the Palatini formulation generates ghost-free and second-order equations that reduce to the GR equations in vacuum. In this context, static spherically symmetric solutions with electric fields generate a plethora of wormhole solutions satisfying the classical energy conditions, and whose properties allow to identify them with the concept of the geon, originally introduced by Wheeler. These solutions provide new insights on the avoidance of spacetime singularities in classical effective geometries.