String Gas Cosmology after Planck

Abstract

We review the status of String Gas Cosmology after the 2015 Planck data release. String gas cosmology predicts an almost scale-invariant spectrum of cosmological perturbations with a slight red tilt, like the simplest inflationary models. It also predicts a scale-invariant spectrum of gravitational waves with a slight blue tilt, unlike inflationary models which predict a red tilt of the gravitational wave spectrum. String gas cosmology yields two consistency relations which determine the tensor to scalar ratio and the slope of the gravitational wave spectrum given the amplitude and tilt of the scalar spectrum. We show that these consistency relations are in good agreement with the Planck data. We discuss future observations which will be able to differentiate between the predictions of inflation and those of string gas cosmology.

Invited review article for the "focus issue" of Classical and Quantum Gravity : "Planck and the fundamentals of cosmology", 17 pages, 3 figures

References in corpus (17)

• A Joint Analysis of BICEP2/Keck Array and Planck Data
• Double Field Theory
• New Ekpyrotic Cosmology
• Generating Ekpyrotic Curvature Perturbations Before the Big Bang
• Tensor Modes from a Primordial Hagedorn Phase of String Cosmology
• Pointer states for primordial fluctuations in inflationary cosmology
• String Gas Cosmology and Structure Formation
• Non-perturbative Gravity, Hagedorn Bounce & CMB
• On the Decoherence of Primordial Fluctuations During Inflation
• Harrison--Zeldovich spectrum from conformal invariance
• Closed String Thermodynamics and a Blue Tensor Spectrum
• Detecting Cosmic Strings in the CMB with the Canny Algorithm
• Stabilizing moduli with thermal matter and nonperturbative effects
• On quantifying and resolving the BICEP2/Planck tension over gravitational waves
• How Likely are Constituent Quanta to Initiate Inflation?
• Inflation Free, Stringy Generation of Scale-Invariant Cosmological Fluctuations in D = 3 + 1 Dimensions
• String Gas Cosmology and Non-Gaussianities

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• Improved DHOST Genesis
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• Constraining the Break of Spatial Diffeomorphism Invariance with Planck Data
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• Quantum gravity and gravitational-wave astronomy
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