Related papers: Sachs-Wolfe effect in space-times with torsion
We show that expanding or contracting Kasner universes are unstable due to the amplification of gravitational waves (GW). As an application of this general relativity effect, we consider a pre-inflationary anisotropic geometry characterized…
In the context of inflationary scenarios, the observed large angle anisotropy of the Cosmic Microwave Background (CMB) temperature is believed to probe the primordial metric perturbations from inflation. Although the perturbations from…
The accretion of the intergalactic medium onto the gaseous disc is used to explain the generation of galactic warps. A cup-shaped distortion is expected, due to the transmission of the linear momentum; but, this effect is small for most…
The impact of large-scale magnetic fields on the interplay between the ordinary and integrated Sachs-Wolfe effects is investigated in the presence of a fluctuating dark energy component. The modified initial conditions of the…
The last phase transition predicted by the standard model of particle physics took place at the QCD scale $T\sim200$ MeV when the universe was about $t\sim10^{-5}$ seconds old and the Hubble radius was around 10 Km. In this paper, we…
We present an analytical derivation of the Sachs Wolfe effect sourced by a primordial magnetic field. In order to consistently specify the initial conditions, we assume that the magnetic field is generated by a causal process, namely a…
This article discusses density perturbations in inflationary models, offering a pedagogical description of how these perturbations are generated by quantum fluctuations in the early universe. A key feature of inflation is that that rapid…
A class of exact, anisotropic cosmological solutions to the vacuum Brans-Dicke theory of gravity is considered within the context of the pre-big bang scenario. Included in this class are the Bianchi type III, V and VI_h models and the…
The first estimation of the energy cascade rate ${|\epsilon_C|}$ of magnetosheath turbulence is obtained using the CLUSTER and THEMIS spacecraft data and an exact law of compressible isothermal magnetohydrodynamics turbulence.…
We review the physics of the Grishchuck-Zel'dovich effect which describes the impact of large amplitude, super-horizon gravitational field fluctuations on the Cosmic Microwave Background anisotropy power spectrum. Using the latest…
Recently, it was proposed that a small true vacuum universe can inflate spontaneously, in principle. Furthermore, there should be matter creation in vacuum inflation due to quantum fluctuations, and the matter created will influence the…
We present limits on the fraction of large angle microwave anisotropies which could come from tensor perturbations. We use the COBE results as well as smaller scale CMB observations, measurements of galaxy correlations, abundances of galaxy…
The Integrated Sachs-Wolfe effect is studied in non-standard cosmologies. By considering flat universes with a non-fluctuating dark energy component, it is shown how the quadrupole power can be suppressed by atypical evolution of the scale…
Cosmological inflation remains to be a unique mechanism of generation of plausible initial conditions in the early universe. In particular, it generates the primordial quasiclassical perturbations with power spectrum determined by the…
We study the effects of long wavelength entropy fluctuations on cosmological probes such as galaxy clustering, luminosity distance, and CMB temperature anisotropies. Specifically, we consider fluctuations of a massless spectator scalar…
We review Gordon's optical metric and the transport equations for the amplitude and polarization of a geometrical optics wave traveling in a gravity field. We apply the theory to the FLRW cosmologies by associating a refraction index with…
We modify Einstein General Relativity by adding non-dynamical scalar fields to account simultaneously for both dark matter and dark energy. The dark energy in this case can be distributed in-homogeneously even within horizon scales. Its…
Gravitational interaction of cosmic microwave background (CMB) photons with matter perturbations present along the line-of-sight to the surface of last scattering modifies the shape of the CMB anisotropy power spectrum. Here I focus on…
We discuss the non-Gaussian contribution to the power spectrum covariance of cosmic microwave background (CMB) anisotropies resulting through weak gravitational lensing angular deflections and the correlation of deflections with secondary…
We study dynamics of entropy perturbations in the two-field assisted dark energy model. Based on the scenario of assisted dark energy, in which one scalar field is subdominant compared with the other in the early epoch, we show that the…