Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

# Cosmology with Variable G and Nonlinear Electrodynamics

Version 1 : Received: 1 July 2020 / Approved: 2 July 2020 / Online: 2 July 2020 (12:56:22 CEST)
Version 2 : Received: 7 July 2020 / Approved: 9 July 2020 / Online: 9 July 2020 (16:02:47 CEST)

How to cite: Joseph, G.W.; Övgün, A. Cosmology with Variable G and Nonlinear Electrodynamics. Preprints 2020, 2020070005 (doi: 10.20944/preprints202007.0005.v1). Joseph, G.W.; Övgün, A. Cosmology with Variable G and Nonlinear Electrodynamics. Preprints 2020, 2020070005 (doi: 10.20944/preprints202007.0005.v1).

## Abstract

In a bid to resolve lingering problems in cosmology, more focus is being tilted towards cosmological models in which physical constants of nature are not necessarily real constants, but varying with cosmic time. In this paper we study cosmology in nonlinear electrodynamics with the Newton's gravitational constant $G$ not a constant but varies with the scale factor of the universe. The evolution of the scale factor $a(t)$ in this model depends on $\alpha$, which gives an steady universe when $\alpha=0.5$. As $\alpha$ increases to $\alpha=1.0, 1.5, 2.0, 3.0$ the universe enter into inflation scenario after that the magnetic monopole field decayed and is converted to radiation. We checked the stability of the model and obtained that it is classically stable with the best condition for the stability at $5/2\geq \alpha >7/4$ .

## Subject Areas

Cosmology; nonlinear electrodynamics; inflation; acceleration of the universe; causality; classical stability; variable $G$

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