Stringy de Sitter Brane-Worlds

2005 ◽  
pp. 261-271
Author(s):  
Tristan Hübsch
Keyword(s):  
De Sitter ◽  
Brane Worlds

scholarly journals de Sitter in non-supersymmetric string theories: no-go theorems and brane-worlds

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Ivano Basile ◽  
Stefano Lanza
Keyword(s):  
Flux Compactifications ◽  
Cosmological Constant ◽  
Dimensional Reduction ◽  
Brane World ◽  
De Sitter ◽  
Top Down ◽  
Brane Worlds ◽  
Concrete Realization ◽  
String Models ◽  
String Theories

Abstract We study de Sitter configurations in ten-dimensional string models where supersymmetry is either absent or broken at the string scale. To this end, we derive expressions for the cosmological constant in general warped flux compactifications with localized sources, which yield no-go theorems that extend previous works on supersymmetric cases. We frame our results within a dimensional reduction and connect them to a number of Swampland conjectures, corroborating them further in the absence of supersymmetry. Furthermore, we construct a top-down string embedding of de Sitter brane-world cosmologies within unstable anti-de Sitter landscapes, providing a concrete realization of a recently revisited proposal.

scholarly journals ACCELERATION OF THE UNIVERSE IN TYPE-0 NONCRITICAL STRINGS

2002 ◽  
Vol 17 (30) ◽  
pp. 4567-4589 ◽  
Author(s):  
G. A. DIAMANDIS ◽  
B. C. GEORGALAS ◽  
N. E. MAVROMATOS ◽  
E. PAPANTONOPOULOS
Keyword(s):  
String Theory ◽  
Extra Dimensions ◽  
Scattering Matrix ◽  
Relative Magnitude ◽  
Observational Evidence ◽  
De Sitter ◽  
Brane Worlds ◽  
Acceleration Of The Universe ◽  
Noncritical Strings ◽  
The Universe

Presently there is preliminary observational evidence that the cosmological constant might be nonzero, and hence that our universe is eternally accelerating (de Sitter). This poses fundamental problems for string theory, since a scattering matrix is not well defined in such universes. In a previous paper we have presented a model, based on (nonequilibrium) noncritical strings, which is characterized by eventual "graceful" exit from a de Sitter phase. The model is based on a type-0 string theory, involving D3 brane worlds, whose initial quantum fluctuations induce the noncriticality. We argue in this paper that this model is compatible with the current observations. A crucial role for the correct "phenomenology" of the model is played by the relative magnitude of the flux of the five-form of the type 0 string to the size of five of the extra dimensions, transverse to the direction of the flux-field. We do not claim, at this stage at least, that this model is a realistic physical model for the universe, but we find it interesting that the model cannot be ruled out immediately, at least on phenomenological grounds.

scholarly journals Excited de Sitter brane worlds localized by a kink

2012 ◽  
Vol 86 (2) ◽  
Author(s):  
Y. Brihaye ◽  
T. Delsate
Keyword(s):  
De Sitter ◽  
Brane Worlds

scholarly journals Gravity in higher codimension de Sitter brane worlds

2003 ◽  
Vol 68 (6) ◽  
Author(s):  
I. Olasagasti ◽  
K. Tamvakis
Keyword(s):  
De Sitter ◽  
Brane Worlds

scholarly journals SCALAR FIELD IN A MINIMALLY COUPLED BRANE WORLD: NO-HAIR AND OTHER NO-GO THEOREMS

2004 ◽  
Vol 13 (04) ◽  
pp. 593-606 ◽  
Author(s):  
K. A. BRONNIKOV ◽  
S. B. FADEEV ◽  
A. V. MICHTCHENKO
Keyword(s):  
Scalar Field ◽  
Strong Field ◽  
Scalar Fields ◽  
Brane World ◽  
Einstein Equations ◽  
De Sitter ◽  
Brane Worlds ◽  
Traversable Wormholes ◽  
Tensor Formula ◽  
Causal Structures

In the brane-world framework, we consider static, spherically symmetric configurations of a scalar field with the Lagrangian (∂ϕ)2/2-V(ϕ), confined on the brane. We use the 4D Einstein equations on the brane obtained by Shiromizu et al., containing the conventional stress tensor [Formula: see text], the tensor [Formula: see text] which is quadratic in [Formula: see text], and [Formula: see text] describing interaction with the bulk. For models under study, the tensor [Formula: see text] has zero divergence, allowing one to consider [Formula: see text]. Such a brane, whose 4D gravity is decoupled from the bulk geometry, may be called minimally coupled. Assuming [Formula: see text], we try to extend to brane worlds some theorems valid for scalar fields in general relativity (GR). Thus, the list of possible global causal structures in all models under consideration is shown to be the same as is known for vacuum with a cosmological constant in GR: Minkowski, Schwarzschild, (anti-) de Sitter and Schwarzschild–(anti-)de Sitter. A no-hair theorem, saying that, given a potential V≥0, asymptotically flat black holes cannot have nontrivial external scalar fields, is proved under certain restrictions. Some objects, forbidden in GR, are allowed on the brane, e.g, traversable wormholes supported by a scalar field, but only at the expense of enormous matter densities in the strong field region.

SELF-CREATING BRANE WORLDS

2004 ◽  
Vol 13 (01) ◽  
pp. 85-106 ◽  
Author(s):  
PEDRO F. GONZÁLEZ-DÍAZ ◽  
JUAN MARTÍN CARRIÓN
Keyword(s):  
Quantum Theory ◽  
Boundary Conditions ◽  
Quantum State ◽  
De Sitter Space ◽  
De Sitter ◽  
Brane Worlds ◽  
Multiply Connected ◽  
Spacetime Structure ◽  
Multiply Connected Region ◽  
The Universe

Several boundary conditions for the universe have been hitherto suggested, basing on different philosophical approaches. In particular, one may choose between the notions that the universe was created either from nothing or by itself. The quantum state of a universe created from nothing has been already formulated under distinct standpoints by Hartle, Hawking, Vilenkin and others. In this paper we have concentrated on deriving a quantum theory for a self-created universe. Thus, we have first considered the spacetime structure of a six-dimensional de Sitter space with a multiply connected region and, by using a cutting and pasting procedure, we have then been able to show that one can introduce a four-brane in such a spacetime whose evolution can also be considered within the context of ekpyrotic and cyclic universes, and quantized in terms of the sum-over-histories formulation, according to the rules of the generalized quantum theory developed by Hartle.

scholarly journals de Sitter and double asymmetric brane worlds

2005 ◽  
Vol 72 (12) ◽  
Author(s):  
Rommel Guerrero ◽  
R. Omar Rodriguez ◽  
Rafael Torrealba
Keyword(s):  
De Sitter ◽  
Brane Worlds

scholarly journals Brane cosmology and the self-tuning of the cosmological constant in the presence of bulk black holes

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
P. Betzios ◽  
O. Papadoulaki
Keyword(s):  
Black Hole ◽  
Cosmological Constant ◽  
Static Solution ◽  
Brane World ◽  
De Sitter ◽  
Brane Cosmology ◽  
Brane Worlds ◽  
Higher Dimensional ◽  
Self Tuning ◽  
Hole Geometry

Abstract Motivated by the holographic self-tuning proposal of the cosmological constant, we generalize and study the cosmology of brane-worlds embedded in a higher-dimensional bulk black hole geometry. We describe the equations and matching conditions in the case of flat, spherical and hyperbolic slicing of the bulk geometry and find the conditions for the existence of a static solution. We solve the equations that govern dynamical geometries in the probe brane limit and we describe in detail the resulting brane-world cosmologies. Of particular interest are the properties of solutions when the brane-world approaches the black hole horizon. In this case the geometry induced on the brane is that of de Sitter, whose entropy and temperature is related to those of the higher dimensional bulk black hole.

Cosmological spacetimes

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Cosmological Model ◽  
Large Scale ◽  
Cosmic Time ◽  
De Sitter ◽  
Matter Distribution ◽  
Observable Universe ◽  
Cosmological Principle ◽  
Riemannian Spacetime ◽  
The Universe ◽  
Copernican Principle

This chapter provides a few examples of representations of the universe on a large scale—a first step in constructing a cosmological model. It first discusses the Copernican principle, which is an approximation/hypothesis about the matter distribution in the observable universe. The chapter then turns to the cosmological principle—a hypothesis about the geometry of the Riemannian spacetime representing the universe, which is assumed to be foliated by 3-spaces labeled by a cosmic time t which are homogeneous and isotropic, that is, ‘maximally symmetric’. After a discussion on maximally symmetric space, this chapter considers spacetimes with homogenous and isotropic sections. Finally, this chapter discusses Milne and de Sitter spacetimes.

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