Fundamental Physics, the Swampland of Effective Field Theory and Early Universe Cosmology

Brandenberger, Robert H.

doi:10.1007/978-3-030-55777-5_37

Cited by 7 publications

(8 citation statements)

References 76 publications

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“…If matter is dominated by winding modes, the Einstein frame metric is static. Thus, these solutions can be viewed as candidates for the emergent universe [41] which SGC posits. In this paper we study some phenomenological consequences of these solutions.…”

Section: Jhep10(2020)155mentioning

confidence: 99%

Solution of the size and horizon problems from classical string geometry

Bernardo

Brandenberger

Franzmann

2020

J. High Energ. Phys.

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Section: Jhep10(2020)155mentioning

confidence: 99%

Solution of the size and horizon problems from classical string geometry

Bernardo

Brandenberger

Franzmann

2020

J. High Energ. Phys.

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“…Thus, we have a time dependent dilaton solution with Minkowski metric in the E-frame. This opens precedent for considering the quasi-static phase required by String Gas Cosmology [20] for the background cosmology and more generally for implementing the emergent scenario advocated in [3] as an alternative to inflation in the context of string cosmology. Both special cases are only possible due to the entire tower of α -corrections, therefore characterizing non-perturbative solutions.…”

Section: Non-perturbative De Sitter (Ds) Solutionsmentioning

confidence: 99%

“…String Gas Cosmology (SGC) [20], for instance, is a toy model that considers the fluctuations to be thermal in their origin, and their stringy nature guarantees them to have a holographic scaling [21,22], while the background evolution is almost quasi-static, H(t) ≈ 0. In more generality, SGC fulfills the requisites demanded by the emergent scenario discussed in [3], which also provides the necessary elements in order to recover an almost scale-invariant P S .…”

Section: Introductionmentioning

confidence: 96%

“…Given current observational windows, what the CMB tells us about the very early universe is encoded into two parameters: the amplitude of these fluctuations, A, and the deviation from scale invariance in their power spectrum, P S , parametrized by the spectral index n s . Neither of them provides us with a direct access to the underlying background dynamics that was evolving these fluctuations before the CMB was emitted [1,2,3].…”

Section: Introductionmentioning

confidence: 99%

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$α'$-Cosmology: solutions and stability analysis

Bernardo,

Franzmann

2020

Preprint

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We review O(d, d) Covariant String Cosmology to all orders in α in the presence of matter and study its solutions. We show that the perturbative analysis for a constant dilaton in the absence of a dilatonic charge does not lead to a time-independet equation of state. Meanwhile, the non-perturbative equations of motion allow de Sitter solutions in the String frame parametrized by the equation of state and the dilatonic charge. Among this set of solutions, we show that a cosmological constant equation of state implies a de Sitter solution both in String and Einstein frames while a winding equation of state implies a de Sitter solution in the former and a static phase in the latter. We also consider the stability of these solutions under homogeneous linear perturbations and show that they are not unstable, therefore defining viable cosmological scenarios.

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“…Recently the dynamics of SGC has been embedded into a more general proposal called Emergent scenario[18].…”

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confidence: 99%

String Cosmology backgrounds from Classical String Geometry

Bernardo,

Brandenberger,

Franzmann

2020

Preprint

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We introduce a very early universe model based on the thermodynamics of a gas of closed strings in a background which is non-perturbative in α . Upon considering the fully α -corrected equations extended to include certain anisotropic cosmological backgrounds, we describe the evolution of the system in three different stages parametrized by the gas' equation of state. Using standard string thermodynamical arguments, we start with an isotropic 10-dimensional universe inside the string scale and evolve it towards a universe with four large spacetime dimensions and six stabilized internal dimensions in the Einstein frame.

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Fundamental Physics, the Swampland of Effective Field Theory and Early Universe Cosmology

Abstract: Assuming that superstring theory is the fundamental theory which unifies all forces of Nature at the quantum level, I argue that there are key limitations on the applicability of effective field theory techniques in describing early universe cosmology.

Cited by 7 publications

References 76 publications

Solution of the size and horizon problems from classical string geometry

Solution of the size and horizon problems from classical string geometry

$α'$-Cosmology: solutions and stability analysis

String Cosmology backgrounds from Classical String Geometry

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