Related papers: Backreaction in late-time cosmology
A simple discussion on the backreaction of inhomogeneities in cosmology, focusing on the possibility that it could explain the present acceleration and solve the coincidence problem.
We address the issue of cosmological backreaction from non-linear structure formation by constructing an approximation for the time evolved metric of a dust dominated universe based on a gradient expansion. Our metric begins as a…
There is an ongoing debate in the literature concerning the effects of averaging out inhomogeneities (``backreaction'') in cosmology. In particular, some simple models of structure formation studied in the literature seem to indicate that…
We evaluate the average expansion rate of a universe which contains a realistic evolving ensemble of non-linear structures. We use the peak model of structure formation to obtain the number density of structures, and take the individual…
A dependence of the neutrino masses on the dark energy scalar field could provide a solution to the why now problem of dark energy. The dynamics of the resulting cosmological model, growing neutrino quintessence, include an attractive force…
This work summarises some of the attempts to explain the phenomenon of dark energy as an effective description of complex gravitational physics and the proper interpretation of observations. Cosmological backreaction has been shown to be…
Dark energy is frequently modelled as an additional dynamical scalar field component in the Universe, referred to as "quintessence", which drives the late-time acceleration. Furthermore, the quintessence field may be coupled to dark matter…
A persistent theme in the study of dark energy is the question of whether it really exists or not. It is often claimed hat we are mis-calculating the cosmological model by neglecting the effects associated with averaging over large-scale…
Recently, we have derived a novel and compact expression for how perturbations in the matter fields of the cosmological fluid can lead to deviations from the standard Friedmann equations. Remarkably, the dissipative damping of velocity…
We perform large-scale cosmological simulations that solve Einstein's equations directly via numerical relativity. Starting with initial conditions sampled from the cosmic microwave background, we track the emergence of a cosmic web without…
Astronomical observations reveal hierarchical structures in the Universe, from galaxies, groups of galaxies, clusters and superclusters, to filaments and voids. On the largest scales it seems that some kind of statistical homogeneity can be…
Every theory that modifies gravity at cosmological distances and that is not already ruled out by the Solar system observations must exhibit some nonlinear mechanism that turns off the modification close to a compact matter source. Given…
Homogeneous and isotropic cosmological models with ordinary matter and gravity predict slower expansion and shorter distances than observed. It is possible that this failure is due the known breakdown of homogeneity and isotropy related to…
When taking the real, inhomogeneous and anisotropic matter distribution in the semi-local universe into account, there may be no need to postulate an accelerating expansion of the universe despite recent type Ia supernova data. Local…
It is known than the inclusion of spatial curvature can modify the evolution of matter perturbations and affect the Large Scale Structure (LSS) formation. We quantify the effects of the non-zero space curvature in terms of LSS formation for…
We present a detailed numerical study of the impact that cosmological models featuring a direct interaction between the Dark Energy component that drives the accelerated expansion of the Universe and Cold Dark Matter can have on the linear…
We investigate the cosmological behavior in a universe governed by time asymmetric extensions of general relativity, which is a novel modified gravity based on the addition of new, time-asymmetric, terms on the Hamiltonian framework, in a…
Cosmological perturbations in an expanding universe back-react on the space-time in which they propagate. Calculations to lowest non-vanishing order in perturbation theory indicate that super-Hubble-scale fluctuations act as a negative and…
This paper investigates the late-time behaviour of certain cosmological models where oscillations play an essential role. Rigorous results are proved on the asymptotics of homogeneous and isotropic spacetimes with a linear massive scalar…
The backreaction of inhomogeneities on the global expansion history of the Universe suggests a possible link of the formation of structures to the recent accelerated expansion. In this paper, the origin of this conjecture is illustrated and…