Related papers: Quantum Creation of a Universe with varying speed …
The tunneling Hamiltonian has proven to be a useful method in many body physics to treat particle tunneling between different states represented as wavefunctions. Here we apply a generalization of the way we formed appropriate wave…
The early cosmic inflation, when taken along with the recent observations that the universe is currently dominated by a low density vacuum energy, leads to at least two potential problems which modern cosmology must address. First, there is…
Some remarkable examples of alternative cosmological theories are reviewed here, ranging from a compilation of variations on the Standard Model through the more distant quasi-steady-state cosmology, plasma cosmology, or universe models as a…
The existence of 'peculiar' velocities due to the formation of cosmic structure marks a point of discord between the real Universe and the usually assumed Friedmann-Lema\'{i}tre-Robertson-Walker metric which accomodates only the smooth…
A standard approach to analyzing tunneling processes in various physical contexts is to use instanton or imaginary time path techniques. For systems in which the tunneling takes place in a time dependent setting, the standard methods are…
Although quintessence cosmologies seem to explain the amount of cosmological constant today, the required conditions are severe. For example, an extremely slowly varying and light scalar field that rolls toward the vanishing vacuum energy…
Loop quantum cosmology predicts that, in simple models, the big bang singularity of classical general relativity is replaced by a quantum bounce. Because of the extreme physical conditions near the bounce, a natural question is whether the…
(Abridged) Does inflation have to happen all in one go? The answer is a resounding no! All cosmological problems can be solved by a sequence of short bursts of cosmic acceleration, interrupted by short epochs of decelerated expansion. The…
We have studied the closed universe model with the variable cosmological term, which is presented as a sum of two terms: Lambda=Lambda_0 -k R. First term Lambda_0 is a constant and it is describing a sum of quantum field's zero…
We investigate spacetimes in which the speed of light along flat 4D sections varies over the extra dimensions due to different warp factors for the space and the time coordinates (``asymmetrically warped'' spacetimes). The main property of…
A mechanism for suppressing the cosmological constant is described, using a superconducting analogy in which fermions coupled to gravitons are in an unstable false vauum. The coupling of the fermions to gravitons and a screened attractive…
We compute the bulk motions of cosmic voids, using a $\Lambda$CDM numerical simulation considering the mean velocities of the dark matter inside the void itself and that of the haloes in the surrounding shell. We find coincident values of…
We study canonical quantization of a closed Euclidean universe with a cosmological constant and a massless scalar field. The closed Euclidean universe with an ordinary matter state can be matched at a finite radius only with the closed…
Brane cosmologies with static, five-dimensional and Z_2 symmetric bulks are analysed. A general solution generating mechanism is outlined. The qualatitive cosmological behaviour of all such solutions is determined. Conditions for avoiding…
We propose that the existence of the string landscape suggests the universe can be in a quantum glass state, where an extremely large viscosity is generated, and long distance dynamics slows down. At the same time, the short distance…
An alternative to the postulate of dark energy required to explain the accelerated expansion of the universe is to adopt an inhomogeneous cosmological model to explain the supernovae data without dark energy. We adopt a void cosmology…
The increasing entropy, large-scale isotropy and approximate flatness of the universe are considered in the context of signature change, which is a classical model of quantum tunnelling in quantum cosmology. The signature change hypothesis…
Density perturbations related to structure formations are expected to be different in dissipative and non-dissipative universes, even if the background evolution of the two universes is the same. To clarify the difference between the two…
We present a cosmological model with a solution that self-accelerates at late-times without signs of ghost instabilities on small scales. The model is a natural extension of the Brans-Dicke (BD) theory including a non-linear derivative…
We discuss models in which vacua other than our own can be directly observed in the present universe. Models with density-dependent vacuum structure can give rise to `non-lethal'-vacua: vacua with lower energy-density than our vacuum, but…