Effects on the CMB from compactification before inflation

Kontou, Eleni-Alexandra; Hertzberg, Mark P.; Masoumi, Ali

doi:10.1088/1475-7516/2017/04/034

Cited by 5 publications

(8 citation statements)

References 29 publications

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“…As a final comment on the field range of φ, we note that the initial condition for φ in the early universe may be in any of the three regimes: small, intermediate, large. The first case arises in string gas cosmology, while the second arises in string inflation, and the latter has been consider as a pre-inflationary state in [32].…”

Section: No Scale Compactificationmentioning

confidence: 99%

Quantum corrections and the de Sitter swampland conjecture

Dasgupta

Emelin

McDonough

et al. 2019

J. High Energ. Phys.

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Recently a swampland criterion has been proposed that rules out de Sitter vacua in string theory. Such a criterion should hold at all points in the field space and especially at points where the system is on-shell. However there has not been any attempt to examine the swampland criterion against explicit equations of motion. In this paper we study four-dimensional de Sitter and quasi-de Sitter solutions using dimensionally reduced M-theory. While on one hand all classical sources that could allow for solutions with de Sitter isometries are ruled out, the quantum corrections, on the other hand, are found to allow for de Sitter solutions provided certain constraints are satisfied. A careful study however shows that generically such a constrained system does not allow for an effective field theory description in four-dimensions. Nevertheless, if some hierarchies between the various quantum pieces could be found, certain solutions with an effective field theory description might exist. Such hierarchies appear once some mild time dependence is switched on, in which case certain quasi-de Sitter solutions may be found without a violation of the swampland criterion.1 It is instructive to speculate on the contribution of classical sources, especially O-planes, in generating de Sitter vacua in string theory. The presence of O-planes essentially involve two regions, one, away from the locations of the O-planes, and two, at the locations of the O-planes. The latter involve singular points and one can remove the singular points from the manifold leaving holes, but then certain boundary terms defined in [3] become non-zero. To obtain the exact values of these terms, one needs to know the metric near the singularity, but since classical gravity breaks down, we cannot evaluate them without incorporating quantum corrections.

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Section: No Scale Compactificationmentioning

confidence: 99%

Quantum corrections and the de Sitter swampland conjecture

Dasgupta

Emelin

McDonough

et al. 2019

J. High Energ. Phys.

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“…Fast roll inflation prior to standard inflation [27,28], bounces and cyclic universes [29][30][31], a radiation dominated era [32,33] and a pre-inflationary matter era supported by primordial micro black holes remnants [34] have been considered in the context of the low quadrupole problem. More recently, slow-roll inflation preceded by a topological defect phase [35] as well as compactification before inflation [36] were also suggested as potential ways to explain the low CMB quadrupole.…”

Section: Introductionmentioning

confidence: 99%

Pre-inflation from the multiverse: can it solve the quadrupole problem in the cosmic microwave background?

et al. 2018

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We analyze a quantized toy model of a universe undergoing eternal inflation using a quantum-field-theoretical formulation of the Wheeler–DeWitt equation. This so-called third quantization method leads to the picture that the eternally inflating universe is converted to a multiverse in which sub-universes are created and exhibit a distinctive phase in their evolution before reaching an asymptotic de Sitter phase. From the perspective of one of these sub-universes, we can thus analyze the pre-inflationary phase that arises naturally. Assuming that our observable universe is represented by one of those sub-universes, we calculate how this pre-inflationary phase influences the power spectrum of the cosmic microwave background (CMB) anisotropies and analyze whether it can explain the observed discrepancy of the power spectrum on large scales, i.e. the quadrupole issue in the CMB. While the answer to this question is negative in the specific model analyzed here, we point out a possible resolution of this issue.

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“…These are sometimes called extra-dimension, or higher dimension, evolution in the string community e.g. [19]. In section 3, we will adapt the theorems in [12] to this situation and present singularity theorems applicable to general warped-product spacetimes.…”

Section: This Papermentioning

confidence: 99%

“…This type of metrics are able to describe "higher-dimension evolutionary" cases and have been considered in the literature to analyze the possibility of viable cosmological models with extra dimensions [10,11], and also in connection with stability issues e.g. [14,23], especially for functions f depending on time, see also [19]. The components of the curvature tensor are readily computed (for instance from (34)(35) in the Appendix) leading to…”

Section: Perturbation: Warped Productsmentioning

confidence: 99%

“…Letγ(u) :x a (u) withN a = dx a (u)/du denote any solution of the equation (17) with initial conditionN a | p = n a , where n a is such thatĝ ab | p n a n b = −f 2 | pḡij n i n j and future pointing. To relate both curvesγ(ū) andγ(u) -so that they provide a null geodesic in the spacetime-set, as in (19), du = f 2 |γdū.…”

Section: The Singularity Theorems Adapted To Warped Productsmentioning

confidence: 99%

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Singularity theorems for warped products and the stability of spatial extra dimensions

Cipriani

Senovilla

2019

J. High Energ. Phys.

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New singularity theorems are derived for generic warped-product spacetimes of any dimension. The main purpose is to analyze the stability of (compact or large) extra dimensions against dynamical perturbations. To that end, the base of the warped product is assumed to be our visible 4-dimensional world, while the extra dimensions define the fibers, hence we consider extra-dimensional evolution. Explicit conditions on the warping function that lead to geodesic incompleteness are given. These conditions can be appropriately rewritten, given a warping function, as restrictions on the intrinsic geometry of the fibers -i.e. the extra dimensional space. To find the results, the conditions for parallel transportation in warped products in terms of their projections onto the base and the fibers have been solved, a result of independent mathematical interest that have been placed on an Appendix.

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Effects on the CMB from compactification before inflation

Cited by 5 publications

References 29 publications

Quantum corrections and the de Sitter swampland conjecture

Quantum corrections and the de Sitter swampland conjecture

Pre-inflation from the multiverse: can it solve the quadrupole problem in the cosmic microwave background?

Singularity theorems for warped products and the stability of spatial extra dimensions

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