Effective field equations and scale-dependent couplings in gravity

Bonanno A. Kofinas G. Zarikas V.
15 May 2021 American Physical Society

Physical Review D
2021 #103 Issue 10

A new set of field equations for a space-time dependent Newtons constant G(x) and cosmological constant Λ(x) in the presence of matter is presented. We prove that it represents the most general mathematically consistent, physically plausible, set of evolution equations assuming at most second derivatives in the dynamical variables. In the new Einsteins equations, only Λ-kinetic terms arise, while in the modified conservation equation, derivative terms of G also appear. As an application, this formalism is applied in the context of the asymptotic safety scenario to the early Universe, assuming a perfect fluid with a radiation equation of state. Cosmological solutions are obtained for all types of spatial curvature, displaying a variety of interesting cosmic evolutions. As an indication of such behaviors, bouncing solutions, recollapsing solutions, or nonsingular expanding solutions with a transient acceleration era are discussed in detail.

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INAF, Osservatorio Astrofisico di Catania, Via S.Sofia 78, Catania, 95123, Italy
INFN, Sezione di Catania, Via S. Sofia 72, Catania, 95123, Italy
Research Group of Geometry, Dynamical Systems and Cosmology, Department of Information and Communication Systems Engineering, University of the Aegean, Karlovassi, Samos, 83200, Greece
Nazarbayev University, School of Engineering, Astana, 010000, Kazakhstan

INAF
INFN
Research Group of Geometry
Nazarbayev University

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