Abstract
We discuss the production of massive relic coherent gravitons in a particular class of ƒ(R) gravity, which arises from string theory, and their possible imprint in the Cosmic Microwave Background. In fact, in the very early Universe, these relic gravitons could have acted as slow gravity waves. They may have then acted to focus the geodesics of radiation and matter. Therefore, their imprint on the later evolution of the Universe could appear as filaments and a domain wall in the Universe today. In that case, the effect on the Cosmic Microwave Background should be analogous to the effect of water waves, which, in focusing light, create optical caustics, which are commonly seen on the bottom of swimming pools. We analyze this important issue by showing how relic massive gravity waves (GWs) perturb the trajectories of the Cosmic Microwave Background photons (gravitational lensing by relic GWs). The consequence of the type of physics discussed is outlined by illustrating an amplification of what might be called optical chaos.
Highlights
Modified gravity currently obtains a lot of attention from the scientific community
The global effect of these variations of the photons’ paths in the Cosmic Microwave Background (CMB) should be analogous to the effect of water waves, which, in focusing light, create optical caustics, which are commonly seen on the bottom of swimming pools
The production of massive relic coherent gravitons in in a particular class of f (R) gravity, which arises from string theory and their possible imprint in the CMB, have been discussed
Summary
Modified gravity currently obtains a lot of attention from the scientific community. The main reason is the remarkable issue that it enables a description of early-time inflation, as well as late-time acceleration epoch (dark energy) in a unified way. One assumes that geometry (for example, the Ricci curvature scalar, R) interacts with material quantum fields, generating back-reactions, which modify the gravitational action, adding interaction terms (examples are high-order terms in the Ricci scalar and/or in the Ricci tensor and non-minimal coupling between matter and gravity). This approach enables the modification of the Lagrangian, with respect to the standard. In the tapestry of f (R) theories, the higher order terms are physically a type of back reaction from geometry acting upon matter, which further modifies geometry This is a topological massive gravity, which represents a form of intrinsic curvature to spacetime. The φμν , which physically contributes to the Wilson integral, has a source term, which is the topological mass
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