Cosmological transitions with changes in the signature of the metric

Sakharov, A. D.

doi:10.3367/ufnr.0161.199105m.0094

Cited by 49 publications

(79 citation statements)

References 7 publications

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“…The value of the cosmological constant Λ originates from an incomplete cancellation between two contributions to energy, a negative one, V AdS < 0, due to the Anti-de Sitter (AdS) minimum used for moduli stabilization, and a positive one, due to an D3-brane. In different parts (or different quantum states) of the universe, the difference between these two may take arbitrary values, but in the part of the universe where we can live it must be extremely small [8][9][10][11][12][13][14][15][16][17][18][19][20],…”

Section: Before Quantum Correctionsmentioning

confidence: 99%

The Landscape, the Swampland and the Era of Precision Cosmology

Akrami

Каллош

Linde

et al. 2018

Fortschritte der Physik

227

229

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We review the advanced version of the KKLT construction and pure d=4 de Sitter supergravity, involving a nilpotent multiplet, with regard to various conjectures that de Sitter state cannot exist in string theory. We explain why we consider these conjectures problematic and not well motivated, and why the recently proposed alternative string theory models of dark energy, ignoring vacuum stabilization, are ruled out by cosmological observations at least at the 3σ level, i.e. with more than 99.7% confidence.

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Section: Before Quantum Correctionsmentioning

confidence: 99%

The Landscape, the Swampland and the Era of Precision Cosmology

Akrami

Каллош

Linde

et al. 2018

Fortschritte der Physik

227

229

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“…−1, and is also different from its asymptotic value w ∞ in the case of Exp-model II. 5 We will discuss this in more detail in the next section.…”

Section: Inflationary and Late-time Dynamicsmentioning

confidence: 99%

“…Arguably, the best presently available theoretical reasoning for the smallness of dark energy is based on anthropic constraints on the energy density of a metastable vacuum state (cosmological constant) [3][4][5][6][7][8][9][10][11], which may take different values in the context of inflationary multiverse (string theory landscape) [4,5,[12][13][14][15]. For a brief review of related ideas see Ref.…”

Section: Introductionmentioning

confidence: 99%

Dark energy, α-attractors, and large-scale structure surveys

Akrami

Каллош

Linde

et al. 2018

J. Cosmol. Astropart. Phys.

134

173

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Over the last few years, a large family of cosmological attractor models has been discovered, which can successfully match the latest inflation-related observational data. Many of these models can also describe a small cosmological constant Λ, which provides the most natural description of the present stage of the cosmological acceleration. In this paper, we study α-attractor models with dynamical dark energy, including the cosmological constant Λ as a free parameter. Predominantly, the models with Λ > 0 converge to the asymptotic regime with the equation of state w = −1. However, there are some models with w = −1, which are compatible with the current observations. In the simplest models with Λ = 0, one has the tensor to scalar ratio r = 12α N 2 and the asymptotic equation of state w = −1 + 2 9α (which in general differs from its present value). For example, in the seven disk M-theory related model with α = 7/3 one finds r ∼ 10 −2 and the asymptotic equation of state is w ∼ −0.9. Future observations, including large-scale structure surveys as well as B-mode detectors will test these, as well as more general models presented here. We also discuss gravitational reheating in models of quintessential inflation and argue that its investigation may be interesting from the point of view of inflationary cosmology. Such models require a much greater number of e-folds, and therefore predict a spectral index n s that can exceed the value in more conventional models by about 0.006. This suggests a way to distinguish the conventional inflationary models from the models of quintessential inflation, even if they predict w = −1.

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“…In this case the construction of wormholes applies to a scale much larger than the Planck length. In this case the wormholes are defined by a transition of the metric similar to that hypothesized in the classical work by Sacharov in 1984 [83].…”

Section: Discussionmentioning

confidence: 74%

General Relativistic Wormhole Connections from Planck-Scales and the ER = EPR Conjecture

Tamburini

Licata

2019

Entropy

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Einstein's equations of general relativity (GR) can describe the connection between events within a given hypervolume of size L larger than the Planck length L P in terms of wormhole connections where metric fluctuations give rise to an indetermination relationship that involves the Riemann curvature tensor. At low energies (when L ≫ L P ), these connections behave like an exchange of a virtual graviton with wavelength λ G = L as if gravitation were an emergent physical property. Down to Planck scales, wormholes avoid the gravitational collapse and any superposition of events or space-times become indistinguishable. These properties of Einstein's equations can find connections with the novel picture of quantum gravity (QG) known as the "Einstein-Rosen (ER)=Einstein-Podolski-Rosen (EPR)" (ER = EPR) conjecture proposed by Susskind and Maldacena in Anti-de-Sitter (AdS) space-times in their equivalence with conformal field theories (CFTs). In this scenario, non-traversable wormhole connections of two or more distant events in space-time through Einstein-Rosen (ER) wormholes that are solutions of the equations of GR, are supposed to be equivalent to events connected with non-local Einstein-Podolski-Rosen (EPR) entangled states that instead belong to the language of quantum mechanics. Our findings suggest that if the ER = EPR conjecture is valid, it can be extended to other different types of space-times and that gravity and space-time could be emergent physical quantities if the exchange of a virtual graviton between events can be considered connected by ER wormholes equivalent to entanglement connections.

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Cosmological transitions with changes in the signature of the metric

Cited by 49 publications

References 7 publications

The Landscape, the Swampland and the Era of Precision Cosmology

The Landscape, the Swampland and the Era of Precision Cosmology

Dark energy, α-attractors, and large-scale structure surveys

General Relativistic Wormhole Connections from Planck-Scales and the ER = EPR Conjecture

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