The Early and Late Universe in the Modified Einstein-Maxwell-Gauss-Bonnet Model

Abstract

This work is aimed at creating and verifying the viability of the Einstein-Gauss-Bonnet model with modifications in the form of the scalar fields and the electromagnetic field. The initial viability analysis of the model confirmed the compliance of the solutions with modern cosmological data. Due to the use of hybrid solutions, the model is universal and can consider a wide range of cases. In this way, it was possible to achieve simultaneous compliance with the conditions of slow-roll and chaotic inflation. The slow-roll parameters meet the requirements of the beginning and duration of inflation. The model fully corresponds to the red tilt of the spectral index \(n_S\) and corresponds to the Planck 2018 data. The propagation speed of scalar perturbations (\(c_A\)) and gravitational waves (\(c_T\)) coincide with the speed of light. Subsequently, an examination of the post-inflationary phase was conducted. The stability of the model is justified by the propagation speed of baryon oscillations. The presence of a transition from decelerated to accelerated expansion was found at the redshift \(z\approx 0.66\). The application of the described methods has shown that the model is stable, viable, and can be used to study the early and late stages of the Universe.