Related papers: The fate of four dimensions
We study the evolution of (phantom) dark energy universe by taking into account the higher-order string corrections to Einstein-Hilbert action with a fixed dilaton. While the presence of a cosmological constant gives stable de-Sitter fixed…
Constructing an explicit compactification yielding a metastable de Sitter (dS) vacuum in a UV consistent string theory is an incredibly difficult open problem. Motivated by this issue, as well as the conjecture that all non-supersymmetric…
Perhaps the greatest challenge for fundamental theories based on compactification from extra dimensions is accommodating a period of accelerated cosmological expansion. Previous studies have identified constraints imposed by the existence…
We argue that $(0,1)$ heterotic string models with 4 non-heterotic spacetime dimensions may provide an instability of the vacuum to gravitational polarization in globally strong gravitational fields. This instability would be triggered…
We study the stability of extra dimensions in string gas cosmology at late times. Vacuum energy and, interestingly, baryons lead to decompactification after they become dynamically important. The string gas can stabilise the effect of…
The discovery of accelerated cosmic expansion implies that, in addition to the attractive gravity of matter, there exists in our universe some other form of energy (dark energy or cosmological constant) producing a repulsive force. The…
In this paper we construct a stringy embedding of the dark bubble model of an expanding 4D cosmology with the help of branes rotating in extra dimensions. The universe rides a bubble which has nucleated in an unstable higher dimensional…
The origin of the observed acceleration of the expansion of the universe is a major problem of modern cosmology and theoretical physics. Simple estimations of the contribution of vacuum to the density energy of the universe in quantum field…
Considering a very large number of extra dimensions, $N\rightarrow \infty$, we show that in the effective four dimensional picture, to leading order in $N$, both the cosmological constant in $N+4$ dimensions and the curvature of the extra…
We consider a massive scalar field with a coordinate-dependent mass in higher-dimensional spacetime. The field satisfies Dirichlet boundary conditions on a brane representing the four-dimensional world. Despite being massive, the theory is…
The smallness of the cosmological constant is one of the basic problems in particle physics and cosmology. Various attempts have been made to explain this mystery, but no satisfactory solution has been found yet. The appearance of extra…
Presently there is preliminary observational evidence that the cosmological constant might be non zero, and hence that our Universe is eternally accelerating (de Sitter). This poses fundamental problems for string theory, since a scattering…
It has recently been conjectured that string theory does not admit de Sitter vacua, and that quintessence explains the current epoch of accelerated cosmic expansion. A proposed, key prediction of this scenario is time-varying couplings in…
We present a new model of dark energy which could explain the observed accelerated expansion of our Universe. We show that a five-dimensional Einstein-Yang-Mills theory defined in a flat Friedmann-Robertson-Walker universe compactified on a…
Modern astronomical observations in cosmology provide increasingly strong evidence that the expansion of the Universe is accelerating. Explanations of the cosmic acceleration within the framework of general relativity use the hypothesis…
It is shown that Einstein gravity in four dimensions with small cosmological constant and small extra dimensions can be obtained by spontaneous compactification of Lovelock gravity in vacuum. Assuming that the extra dimensions are compact…
The consequences of noncommutativity of space coordinates of string theory in the proposed large extra dimension solution to the hierarchy problem are explored; in particular the large dimension stabilization and the graviton reabsorption…
Homogeneous cosmological solutions are obtained in five dimensional space time assuming equations of state $ p = k\rho $ and $ p_{5}= \gamma\rho$ where p is the isotropic 3 - pressure and $p_{5}$, that for the fifth dimension. Using…
We consider multidimensional gravitational models with a nonlinear scalar curvature term and form fields in the action functional. In our scenario it is assumed that the higher dimensional spacetime undergoes a spontaneous compactification…
The idea of extra-dimensions has recently gone through a renewal with the hypothesis, suggested by recent developments in string theory, that ordinary matter is confined to a sub-space, called brane, embedded in a higher dimensional…