Dark Radiation and the Hagedorn Phase

Abstract

We point out that if the sector associated with the Standard Model degrees of freedom entered an open string Hagedorn phase in the early universe while the dark radiation sector was not part of this plasma, then this can lead to low values of the observable $\Delta N_{\text{eff}}$ (number of additional neutrinolike species) from the dark radiation. For explicit analysis, we focus on warped string compactifications with the Standard Model degrees of freedom at the bottom of a warped throat. If the Hubble scale during inflation is above the warped string scale associated with the throat, then the Standard Model sector will enter the Hagedorn phase. In this scenario, bulk axions are no longer dangerous from the point of view of dark radiation. While this article focuses on warped compactifications, the basic idea can be relevant to any scenario where the early universe entered a Hagedorn phase.

arXiv commentv2. 7pp double-columned, somewhat improved discussion, minor clarifications, matches published version up to typography/formatting

References in corpus (38)

• A Large Mass Hierarchy from a Small Extra Dimension
• Hierarchies from Fluxes in String Compactifications
• String Axiverse
• Planck 2018 results. I. Overview and the cosmological legacy of Planck
• Big Bang Nucleosynthesis: 2015
• Model Independent Properties and Cosmological Implications of the Dilaton and Moduli Sectors of 4-d Strings
• Cosmological Implications of Dynamical Supersymmetry Breaking
• De Sitter Space and the Swampland
• CMB-S4 Science Book, First Edition
• Trans-Planckian Censorship and the Swampland
• Producing a Scale-Invariant Spectrum of Perturbations in a Hagedorn Phase of String Cosmology
• Brane Gases in the Early Universe
• Inflation from Warped Space
• Dark Radiation in LARGE Volume Models
• Supersymmetric Pati-Salam Models from Intersecting D6-branes: A Road to the Standard Model
• Dark Radiation and Dark Matter in Large Volume Compactifications
• Stringy Effects During Inflation and Reheating
• On String Theory Expectations for Photon Couplings to Axion-Like Particles
• String Thermodynamics in D-Brane Backgrounds
• Moduli-Induced Axion Problem
• The Ubiquitous Throat
• Correlation between Dark Matter and Dark Radiation in String Compactifications
• Touring the Hagedorn Ridge
• Completion of standard-like embeddings
• Moduli Vacuum Misalignment and Precise Predictions in String Inflation
• The lightest visible-sector supersymmetric particle is likely to be unstable
• A Monte Carlo exploration of threefold base geometries for 4d F-theory vacua
• Dark Radiation predictions from general Large Volume Scenarios
• Reheating and Dark Radiation after Fibre Inflation
• Dark Radiation in Anisotropic LARGE Volume Compactifications
• General Analysis of Dark Radiation in Sequestered String Models
• Moduli Stabilisation and the Statistics of Axion Physics in the Landscape
• Strings and D-Branes at High Temperature
• Cosmology in the presence of multiple light moduli
• Loop corrections to Delta N_eff in large volume models
• The Axiverse induced Dark Radiation Problem
• Topological Gravity as the Early Phase of Our Universe
• Anthropic Bound on Dark Radiation and its Implications for Reheating

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