Related papers: Smooth Cosmologies from M-theory
We obtain D=6, N=(1,1) de Sitter supergravity from a hyperbolic reduction of the massive type IIA* theory. We construct a smooth cosmological solution in which the co-moving time runs from an infinite past, which is dS_4\times S^2, to an…
The torsion is shown to be vitally important in the explanation of the evolution of the universe in a large class of gravitational theories containing quadratic terms of curvature and torsion. The cosmological solutions with homogeneous and…
We obtain D=4 de Sitter gravity coupled to SU(2) Yang-Mills gauge fields from an explicit and consistent truncation of D=11 supergravity via Kaluza-Klein dimensional reduction on a non-compact space. The ``internal'' space is a smooth…
A complete global analysis of spatially-flat, four-dimensional cosmologies derived from the type IIA string and M-theory effective actions is presented. A non--trivial Ramond-Ramond sector is included. The governing equations are written as…
Decaying vacuum cosmological models evolving smoothly between two extreme (very early and late time) de Sitter phases are capable to solve or at least to alleviate some cosmological puzzles, among them: (i) the singularity, (ii) horizon,…
Two ways in which de Sitter space can arise in supergravity theories are discussed. In the first, it arises as a solution of a conventional supergravity, in which case it necessarily has no Killing spinors. For example, de Sitter space can…
We obtain the general cosmological evolution equations for a classically consistent theory of bimetric gravity. Their analytic solutions are demonstrated to generically allow for a cosmic evolution starting out from a matter dominated FLRW…
We study aspects of the accelerating cosmologies obtained from the compactification of vacuum solution and S2-branes of superstring/M theories. Parameter dependence of the resulting expansion of our universe and internal space is examined…
We study slow-roll accelerating cosmologies arising from geometric compactifications of type IIA string theory on $T^{6}/(\mathbb{Z}_{2}\,\times\,\mathbb{Z}_{2})$. With the aid of a genetic algorithm, we are able to find quasi-de Sitter…
We point out that the solution of $(4+n)$-dimensional gravity coupled to the dilaton and an $n$-form field strength can give rise to a flat 4-dimensional universe (with a scale factor) of the type proposed recently under time dependent…
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…
In this note we study a massive IIA supergravity theory obtained in hep-th/9707139 by compactification of M-theory. We point out that de Sitter space in arbitrary dimensions arises naturally as the vacuum of this theory. This explicitly…
From four-dimensional $N=4$ matter-coupled gauged supergravity, we study smooth time-dependent cosmological solutions interpolating between a $dS_2\times \Sigma_2$ spacetime, with $\Sigma_2 = S^2$ and $H^2$, in the infinite past and a…
We present some exact scalar potentials for the dimensionally reduced theory and examine the possibility of obtaining accelerating 4d cosmology from String/M-theory, more generally, hyperbolic and flux compactification. In the hyperbolic…
We study, using Mean Curvature Flow methods, 3+1 dimensional cosmologies with a positive cosmological constant, matter satisfying the dominant and the strong energy conditions, and with spatial slices that can be foliated by 2-dimensional…
In this work, which is a follow-up of arXiv:2102.06512, we document new cosmological solutions from four-dimensional $N=4$ matter-coupled supergravity. The solutions smoothly interpolate between a $dS_2\times S^2$ spacetime at $t\rightarrow…
We have investigated the cosmological scenarios with a four dimensional effective action which is connected with multidimensional, supergravity and string theories. The solution for the scale factor is such that initially universe undergoes…
Motivated by the recently proposed bounds on the slow-roll parameters for scalar potentials arising from string/M-theory compactifications, a.k.a. the Refined de Sitter Swampland conjecture, we explore the sharpness of such constraints…
We use the superspace formulation of (massive) IIA supergravity to obtain the explicit form of the dilatino terms, and we find that the quartic-dilatino term is positive. The theory admits a ten-dimensional de Sitter solution, obtained by…
A new cosmological model based on the de Sitter gauge theory (dSGT) is studied in this paper. By some transformations, we find, in the dust universe, the cosmological equations of dSGT could form an autonomous system. We conduct dynamics…