Related papers: Accelerating expansion and change of signature
The model where the universe is considered as an expanding spherical 3-brane allows us to explain its expansion rate without a dark energy component. In this scenario the computed redshift that corresponds to the transition from cosmic…
We show that the accelerated expansion of the Universe can be viewed as a crossover phenomenon where the Newton constant and the Cosmological constant are actually scaling operators, dynamically evolving in the attraction basin of a…
In this note we consider the spontaneous creation of the brane world in five-dimensional space with nondynamical external four-form field via spherically asymmetric bounce solution. We argue that spherically asymmetric bounce suggests…
If the equation of state for "dark energy" varies periodically, the expansion of the Universe may have undergone alternating eras of acceleration and deceleration. We examine a specific form that survives existing observational tests, does…
The cosmology of the Randall-Sundrum scenario for a positive tension brane in a 5-D Universe with localized gravity has been studied extensively recently. Here we extend it to more general situations. We consider the time-dependent…
We describe spontaneous creation of the Brane World in $AdS_{5}$ with external field. The resulting Brane World consists of a flat 4d spatially finite expanding Universe and curved expanding "regulator" branes. No negative tension branes…
Braneworld theory provides a natural setting to treat, at a classical level, the cosmological effects of vacuum energy. Non-static extra dimensions can generally lead to a variable vacuum energy, which in turn may explain the present…
Following the observational evidence for cosmic acceleration which may exclude a possibility for the universe to recollapse to a second singularity, we review alternative scenarios of its future evolution. Although the de Sitter asymptotic…
Modern data is showing increasing evidence that the Universe is accelerating. So far, all attempts to account for the acceleration have required some fundamental dimensionless quantities to be extremely small. We show how a class of scalar…
In the braneworld scenario, we introduce a uniformly distributed cloud of infinitely long strings in the five dimensional AdS bulk spacetime. The end points of the strings are attached to the brane and becomes the source of the four…
We consider finite-time, future (sudden or Big Rip type) singularities which may occur even when strong energy condition is not violated but equation of state parameter is time-dependent. Recently, example of such singularity has been…
We construct an eternally inflating spacelike brane world model. If the space dimension of the brane is three (SM2) or six (SM5) for M theory or four (SD3) for superstring theory, a time-dependent $n$-form field would supply a constant…
The purpose of the paper is five-fold: (a) Argue that the question in the title can be presented in a meaningful manner and that it requires an answer. (b) Discuss the conventional answers and explain why they are unsatisfactory. (c)…
The acceleration of the expansion of the universe represents one of the major challenges to our current understanding of fundamental physics. In principle, to explain this phenomenon, at least two different routes may be followed: either…
In this paper we consider some constraints on brane-world cosmologies. In the first part we analyze different behaviors for the expansion of our universe by imposing constraints on the speed of sound. In the second part, we study the nature…
The ultimate fate of life in a universe with accelerated expansion is considered. Previous work showed that life cannot go on indefinitely in a universe dominated by a cosmological constant. In this paper we consider instead other models of…
Recently it was observed that the hyperbolic compactification of M/string theory related to S-branes may lead to a transient period of acceleration of the universe. We study time evolution of the corresponding effective 4d cosmological…
The discovery of accelerated expansion of the universe opened the possibility of new scenarios for the doom of our spacetime, besides aeternal expansion and a final contraction. In this paper we review the chances which may await our…
Fate of branes in external fields is reviewed. Spontaneous creation of the Brane World in $AdS_{5}$ with external field is described. The resulting Brane World consists of a flat 4d spatially finite expanding Universe and curved expanding…
A brane universe moving in a curved higher dimensional bulk space is considered. The motion induces a cosmological evolution on the universe brane that is indistiguishable from a similar one induced by matter density on the brane. The…