相关论文: Effective Equation of State Oscillations at Matter…
A generic feature of viable $F(R)$ gravity is investigated: It is demonstrated that during the matter dominated era the large frequency oscillations of the effective dark energy may influence the behavior of higher derivatives of the Hubble…
The vacuum $R^2$ model is known to generate a quasi-de Sitter evolution for inflation, using solely the slow-roll assumptions. Using standard reconstruction techniques, we demonstrate that the $f(R)$ gravity which actually realizes the…
A class of viable $F(R)$ gravity models which can provide a unified description of inflation with the dark energy era is confronted with the latest observational data on the dark energy era. These models have the unique characteristic that…
In this work we study certain classes of $F(R,{\cal G})$ gravity which have appealing phenomenological features, with respect to the successful realization of the dark energy and of the inflationary era. Particularly, we discuss the general…
In this work we construct a formalism that can reveal the general characteristics of classes of viable $F(R)$ inflationary theories. The assumptions we make is that the slow-roll era occurs, and that the de Sitter scalaron mass $m^2(R)$ of…
We present a model of $F(R)$ gravity in the presence of a string theory motivated misalignment axion like particle materialized in terms of a canonical scalar field minimally coupled with gravity, and we study the cosmological phenomenology…
Two $F(R)$ gravity models are tested on the basis of their viability during all stages of cosmological evolution. It is shown that these models can describe both the early-time inflationary epoch and the dark energy epoch. The models are…
This paper is devoted to the analysis of a class of $F(R)$ gravity, where additional logarithmic corrections are assumed. The gravitational action includes an exponential term and a $R^2$ inflationary term, both with logarithmic…
In this paper we investigate how to describe in a unified way a constant-roll inflationary era with a dark energy era, by using the theoretical framework of $F(R)$ gravity. To this end, we introduce some classes of appropriately chosen…
In this work we shall study the late-time dynamics of several $F(R)$ gravity models. By appropriately expressing the field equations in terms of the redshift and of a statefinder function, we shall solve numerically the field equations…
We consider a class of exponential models of $f(R)$ gravity, in the presence of a canonical scalar field, for which at early times the effective Lagrangian of the theory becomes that of a rescaled canonical scalar field with the…
In this work we examine a theoretical scenario which combines two fundamental theoretical proposals for the early Universe and a possible evolution for the early post-inflationary epoch. Specifically, we assume that the early Universe…
In order to describe inflation in general relativity, scalar fields must inevitably be used, with all the setbacks of that description. On the other hand, $f(R)$ gravity and other modified gravity theories seem to provide a unified…
In this work we examine the effects of a pre-inflationary de Sitter bounce on the energy spectrum of the primordial gravitational waves. Specifically we assume that the Universe is described by several evolution patches, starting with a de…
We provide a theoretical model of $F(R)$ gravity in which it is possible to describe in a unified way inflation, an early and a late dark energy era, in the presence of a light axion particle which plays the role of the dark matter…
The empty space (with no matter fields) is not really empty because of natural metric fluctuations, quantum and classical. We show that gravitons as well as classical gravitational waves of super-horizon wavelengths are able to form the de…
In this work we shall develop a quantitative approach for extracting predictions on the primordial gravitational waves energy spectrum for $f(R)$ gravity. We shall consider two distinct models which yield different phenomenology, one pure…
The $f(R)$ Modified Gravity is a modification of Einstein's general theory of relativity, which aims to explain issues beyond The Standard Model of Cosmology such as dark energy and dark matter. As a theory of gravitation that govern major…
In this seven-part paper, we show that gravitational waves (classical and quantum) produce the accelerated de Sitter expansion at the start and at the end of the cosmological evolution of the Universe. In these periods, the Universe…
Recently, a combined model of the primordial inflation and the present cosmic acceleration has been proposed in the context of f(R) gravity. This model is composed of the late-time acceleration term and an R2 term, which enables the model…