Related papers: Backreaction effects on the matter side of Einstei…
The gravitational field equations on cosmological scales are obtained by averaging the Einstein field equations of general relativity. By assuming spatial homogeneity and isotropy on the largest scales, the local inhomogeneities affect the…
We investigate the characteristic modifications in the evolving cosmological perturbations when dark energy interacts with dust-like matter, causing the latter's background energy density fall off with time faster than usual. Focusing in…
The universe is smooth on large scales but very inhomogeneous on small scales. Why is the spacetime on large scales modeled to a good approximation by the Friedmann equations? Are we sure that small-scale non-linearities do not induce a…
A general equation of state is used to model unified dark matter and dark energy (dark fluid), and it has been proved that this model is equivalent to a single fluid with time-dependent bulk viscosity. In this paper, we investigate scalar…
Motivated by the swampland conjectures, we study cosmological signatures of a quintessence potential which induces time variation in the low energy effective field theory. After deriving the evolution of the quintessence field, we…
In a recent paper we showed that a quintessence scalar field plus a dissipative matter fluid can drive late cosmic accelerated expansion and simultaneously solve the coincidence problem [1]. In this brief report we extend this result to the…
We discuss briefly discrete space effects and show that this leads to space reflection asymmetry and also a minor modification of Einstein's energy-mass formula.
It is shown that quantum vacuum fluctuations give rise to a curvature of space-time of the order appropriate to explain the observed accelerated expansion of the universe. The fact that the fluctuations produce curvature, even if the…
We discuss a cosmology in which cold dark-matter particles decay into relativistic particles. We argue that such decays could lead naturally to a bulk viscosity in the cosmic fluid. For decay lifetimes comparable to the present hubble age,…
The EDGES experiment has detected the global absorption signal of 21 cm line at $z\sim17$ in cosmic dawn era and reported its amplitude larger than the standard cosmological prediction. One of the possible explanation requires that the…
The effective theory of large-scale structure formation based on $\Lambda$CDM paradigm predicts finite dissipative effects in the resulting fluid equations. In this work, we study how viscous effect that could arise if one includes…
In the context of second order perturbation theory, cosmological backreaction is seen to rescale both time and the scale factor. The issue of the homogeneous limit of long-wavelength perturbations is addressed and backreaction is quantified…
We use numerical relativity to study the violent preheating era at the end of inflation. This epoch can result in highly nonlinear fluctuations in density and gravitational potential which feed back onto the averaged expansion rate -- an…
We calculate a general effective stress-energy tensor induced by cosmological inhomogeneity in effective theories of gravity where the action is Taylor-expandable in the Riemann tensor and covariant derivatives of the Riemann tensor. This…
Until recently the study of the gravitational field of dark matter was primarily concerned with its local effects on the motion of stars in galaxies and galaxy clusters. On the other hand, the WMAP experiment has shown that the…
Cosmological backreaction suggests a link between structure formation and the expansion history of the Universe. In order to quantitatively examine this connection, we dynamically investigate a volume partition of the Universe into over--…
Cosmic backreaction as an additional source of the expansion of the universe has been a debate topic since the discovery of cosmic acceleration. The major concern is whether the self interaction of small-scale nonlinear structures would…
The problem of corrections to Einstein's equations arising from averaging of inhomogeneities ("backreaction") in the cosmological context, has gained considerable attention recently. We present results of analysing cosmological perturbation…
Prompted by the recent more precise determination of the basic cosmological parameters and growing evidence that the matter-energy content of the universe is now dominated by dark energy and dark matter we present the general solution of…
All observational evidence for dark matter and dark energy is so far exclusively gravitational. Hence, the dark sector may be equivalently described by a theory of the spacetime metric whose dynamics is affected by interactions with an…