Related papers: Dynamically avoiding fine-tuning the cosmological …
The dilaton-gravity sector of the Two Measures Field Theory (TMT)is explored in detail in the context of cosmology. The model possesses scale invariance which is spontaneously broken due to the intrinsic features of the TMT dynamics. The…
A mechanism for suppressing the cosmological constant is developed, based on an analogy with a superconducting phaseshift in which free fermions coupled perturbatively to a weak gravitational field are in an unstable false vacuum state. The…
In this paper, we investigate the theoretical possibility that a Lagrangian fixed point, when applied to cosmological models, can drive dynamical evolution towards a bouncing universe. We analyze the physics of a Lagrangian fixed point…
We study the problem of relaxing a large cosmological constant in the astrophysical domain through a dynamical mechanism based on a modified action of gravity previously considered by us at the cosmological level. We solve the model in the…
Observation indicates that the expansion of the Universe is accelerating and favours a dynamical cosmological constant, \Lambda(t). We consider the possibility that this is due to a scalar field which has undergone a very recent phase…
A model for a flat isotropic universe with a negative cosmological constant $\Lambda$ and a massless scalar field as sole matter content is studied within the framework of Loop Quantum Cosmology. By application of the methods introduced for…
On the basis of qualitative theory of differential equations it is shown that dynamic system based on the system of Einstein - Klein - Gordon equations with regard to Friedman Universe has a stable center corresponding to zero values of…
We consider a model belonging to the class of gravities with dynamical torsion. The model is free of ghosts and gradient instabilities about Minkowski and torsionless Einstein backgrounds. We find that at zero cosmological constant, the…
In this work we propose a new general model of eternal cyclic Universe. We start from the assumption that quantum gravity corrections can be effectively accounted by the addition of higher order curvature terms in the Lagrangian density for…
A phenomenological formalism is presented in which the apparent acceleration of the universe is generated by large-scale structure formation, thus eliminating the magnitude and coincidence fine-tuning problems of the Cosmological Constant…
Exact cosmological solutions for effective actions in D dimensions inspired by the tree-level superstring action are studied. For a certain range of free parameters existing in the model, nonsingular bouncing solutions are found. Among…
In this study, by revisiting the quantum interpretation of the cosmological constant, we introduce its formal representation within standard General Relativity. Examining its behavior in a Friedmann-Robertson-Walker spacetime reveals a…
The cosmological constant term (CC), $\Lambda$, is a pivotal ingredient in the standard model of cosmology or $\Lambda$CDM, but it is a rigid quantity for the entire cosmic history. This is unnatural and inconsistent. Different theoretical…
We investigate the effects of scale-free model on cosmology, providing, in this way, a statistical background in the framework of general relativity. In order to discuss properties and time evolution of some relevant universe dynamical…
In this paper we investigate dynamics of the modified loop quantum cosmology models using dynamical systems methods. Modifications considered come from the choice of the different field strength operator $\hat{F}$ and result in different…
To seek for a singularity free model universe from a perfect fluid scalar-metric cosmology, we work in the "\emph{Emergent Cosmology}" (EC) paradigm which is a non-singular alternative for cosmological inflation. By using two methods…
In the context of the so-called Gauss-Bonnet gravity, where the gravitational action includes function of the Gauss-Bonnet invariant, we study cosmological solutions, especially the well-known $\Lambda$CDM model. It is shown that the dark…
The dynamics of a (3 + 1) dimensional homogeneous anisotropic universe is modified by Loop Quantum Cosmology and, consequently, it has generically a big bounce in the past instead of a big-bang singularity. This modified dynamics can be…
We point out that $\Lambda$CDM cosmology has an ignored assumption. That is, the $\Lambda$ component of the universe moves synchronously with ordinary matters on Hubble scales. If cosmological constant is vacuum energy, this assumption may…
We propose a model for early universe cosmology without the need for fundamental scalar fields. Cosmic acceleration and phenomenologically viable reheating of the universe results from a series of energy transitions, where during each…