Abundance and properties of dark radiation from the cosmic microwave background

Abstract

We study the cosmological signatures of new light relics that are collisionless like standard neutrinos or are strongly interacting. We provide a simple and succinct rephrasing of their physical effects in the cosmic microwave background, as well as the resulting parameter degeneracies with other cosmological parameters, in terms of the total radiation abundance and the fraction thereof that freely streams. In these more general terms, interacting and noninteracting light relics are differentiated by their respective decrease and increase of the free-streaming fraction, and, moreover, the scale-dependent interplay thereof with a common, correlated reduction of the fraction of matter in baryons. We then derive updated constraints on various dark-radiation scenarios with the latest cosmological observations, employing this language to identify the physical origin of the impact of each dataset. The "PR4" reanalyses of Planck CMB data prefer a larger primordial helium yield and therefore also slightly more radiation than the 2018 analysis; we investigate the differences between the two releases that drives these shifts. Smaller free-streaming fractions are disfavored by the excess lensing of the CMB measured in lensing reconstruction data from Planck and the Atacama Cosmology Telescope. On the other hand, baryon acoustic oscillation measurements from the Dark Energy Spectroscopic Instrument drive marginal detections of new, strongly interacting light relics due to that data's preference for lower matter fractions. Finally, we forecast measurements from the CMB-S4 experiment.

arXiv comment31+10 pages, 22 figures. v2: minor revisions and additional explanations

References in corpus (95)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results
• The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological analysis of the DR12 galaxy sample
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results
• The Cosmic Linear Anisotropy Solving System (CLASS) II: Approximation schemes
• A Comprehensive Measurement of the Local Value of the Hubble Constant with 1 km/s/Mpc Uncertainty from the Hubble Space Telescope and the SH0ES Team
• Baryonic Features in the Matter Transfer Function
• The Clustering of the SDSS DR7 Main Galaxy Sample I: A 4 per cent Distance Measure at z=0.15
• Cosmological Perturbation Theory in the Synchronous and Conformal Newtonian Gauges
• Cosmological Perturbation Theory in the Synchronous vs. Conformal Newtonian Gauge
• The Cosmic Microwave Background Spectrum from the Full COBE/FIRAS Data Set
• The Simons Observatory: Science goals and forecasts
• The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Cosmological Implications from two Decades of Spectroscopic Surveys at the Apache Point observatory
• The Temperature of the Cosmic Microwave Background
• Planck 2018 results. V. CMB power spectra and likelihoods
• DESI 2024 VI: Cosmological Constraints from the Measurements of Baryon Acoustic Oscillations
• Small Scale Cosmological Perturbations: An Analytic Approach
• Conservative Constraints on Early Cosmology: an illustration of the Monte Python cosmological parameter inference code
• Cobaya: Code for Bayesian Analysis of hierarchical physical models
• The Hubble Hunter's Guide
• The Atacama Cosmology Telescope: DR4 Maps and Cosmological Parameters
• Efficient sampling of fast and slow cosmological parameters
• Sterile Neutrino Hot, Warm, and Cold Dark Matter
• The Cosmic Linear Anisotropy Solving System (CLASS) I: Overview
• A CMB Polarization Primer
• Structure Formation with Generalized Dark Matter
• The Cosmic Linear Anisotropy Solving System (CLASS) IV: Efficient implementation of non-cold relics
• Signatures of Relativistic Neutrinos in CMB Anisotropy and Matter Clustering
• The Neutrino Puzzle: Anomalies, Interactions, and Cosmological Tensions
• The Atacama Cosmology Telescope: DR6 Gravitational Lensing Map and Cosmological Parameters
• The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: measurement of the BAO and growth rate of structure of the luminous red galaxy sample from the anisotropic correlation function between redshifts 0.6 and 1
• The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: measurement of the BAO and growth rate of structure of the luminous red galaxy sample from the anisotropic power spectrum between redshifts 0.6 and 1.0
• How Massless Neutrinos Affect the Cosmic Microwave Background Damping Tail
• Neutrino decoupling including flavour oscillations and primordial nucleosynthesis
• The Atacama Cosmology Telescope: A Measurement of the DR6 CMB Lensing Power Spectrum and its Implications for Structure Growth
• DESI 2024 III: Baryon Acoustic Oscillations from Galaxies and Quasars
• Accurate halo-model matter power spectra with dark energy, massive neutrinos and modified gravitational forces
• DESI 2024 IV: Baryon Acoustic Oscillations from the Lyman Alpha Forest
• The Python Sky Model: software for simulating the Galactic microwave sky
• CMB power spectra and cosmological parameters from Planck PR4 with CamSpec
• Non-linear perturbation theory extension of the Boltzmann code CLASS
• Cosmological parameters derived from the final (PR4) Planck data release
• Goldstone Bosons as Fractional Cosmic Neutrinos
• Non-Abelian dark matter and dark radiation
• DESI 2024 VII: Cosmological Constraints from the Full-Shape Modeling of Clustering Measurements
• Interacting Dark Sector and Precision Cosmology
• Analytic approach to the polarization of the cosmic microwave background in flat and open universes
• Phases of New Physics in the CMB
• A First Detection of the Acoustic Oscillation Phase Shift Expected from the Cosmic Neutrino Background
• Limits on Neutrino-Neutrino Scattering in the Early Universe
• A New Target for Cosmic Axion Searches
• Updated constraints on non-standard neutrino interactions from Planck
• Constraining Dark Matter-Neutrino Interactions using the CMB and Large-Scale Structure
• A tale of two modes: Neutrino free-streaming in the early universe
• Cosmological Signatures of Interacting Neutrinos
• Pseudoscalar - sterile neutrino interactions: reconciling the cosmos with neutrino oscillations
• Updated constraints on massive neutrino self-interactions from cosmology in light of the $H_0$ tension
• New Bounds for Axions and Axion-Like Particles with keV-GeV Masses
• Interacting radiation after Planck and its implications for the Hubble Tension
• Searching for Light Relics with Large-Scale Structure
• Thermal Dark Matter Below an MeV
• A Hidden Dark Matter Sector, Dark Radiation, and the CMB
• Phases of New Physics in the BAO Spectrum
• Cosmological constraints on neutrino self-interactions with a light mediator
• First Constraint on the Neutrino-Induced Phase Shift in the BAO Spectrum
• Cosmological Constraints on Interacting Light Particles
• CMB Delensing Beyond the B Modes
• Boltzmann hierarchy for interacting neutrinos I: formalism
• $\Lambda$CDM or self-interacting neutrinos? - how CMB data can tell the two models apart
• Massive neutrinos and cosmic composition
• Flavor-specific Interaction Favors Strong Neutrino Self-coupling in the Early Universe
• Robustness of baryon acoustic oscillation constraints for early-Universe modifications to $\Lambda$CDM
• Wandering in the Background: A CMB Explorer
• Constraints on secret neutrino interactions after Planck
• Joint CMB and BBN Constraints on Light Dark Sectors with Dark Radiation
• Probing Decoupling in Dark Sectors with the Cosmic Microwave Background
• Massive neutrino self-interactions and inflation
• Cosmology with varying fundamental constants from hyperlight, coupled scalars
• Self-Interacting Neutrinos in Light of Large-Scale Structure Data
• Self-interacting Dark Radiation
• The two-mode puzzle: Confronting self-interacting neutrinos with the full shape of the galaxy power spectrum
• Confronting interacting dark radiation scenarios with cosmological data
• Constraining Models of Neutrino Mass and Neutrino Interactions with the Planck Satellite
• Cosmic Microwave Background Acoustic Peak Locations
• Scaling Transformations and the Origins of Light Relics Constraints from Cosmic Microwave Background Observations
• Global view of neutrino interactions in cosmology: The freestreaming window as seen by Planck
• Probing neutrino interactions and dark radiation with gravitational waves
• Dark Radiation from Neutrino Mixing after Big Bang Nucleosynthesis
• Strong constraints on a simple self-interacting neutrino cosmology
• Fiducial-Cosmology-dependent systematics for the DESI 2024 BAO Analysis
• Resonant neutrino self-interactions and the $H_0$ tension
• Was Entropy Conserved between BBN and Recombination?
• The Phase of the BAO on Observable Scales
• Comprehensive Constraints on Dark Radiation Injection After BBN

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