Return of Harrison-Zeldovich spectrum in light of recent cosmological tensions

Abstract

The spectral index $n_s$ of scalar perturbation is the significant initial condition set by inflation theory for our observable Universe. According to Planck results, current constraint is $n_s=0.965\pm 0.004$, while an exact scale-invaiant Harrison-Zeldovich spectrum, i.e. $n_s=1$, has been ruled out at $8.4\sigma$ significance level. However, it is well-known that the standard $\Lambda$CDM model is suffering from the Hubble tension, which is at $\sim 5\sigma$ significance level. This inconsistency likely indicates that the comoving sound horizon at last scattering surface is actually lower than expected, which so seems to be calling for the return of $n_s=1$. Here, in light of recent observations we find strong evidence for a $n_s=1$ Universe. And we show that if so, it would be confirmed conclusively by CMB-S4 experiment.

6 pages, 5 figures

References in corpus (36)

• 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
• In the Realm of the Hubble tension $-$ a Review of Solutions
• The Clustering of the SDSS DR7 Main Galaxy Sample I: A 4 per cent Distance Measure at z=0.15
• Bayes in the sky: Bayesian inference and model selection in cosmology
• Dark Energy Survey Year 3 Results: Cosmological Constraints from Galaxy Clustering and Weak Lensing
• BICEP / Keck XIII: Improved Constraints on Primordial Gravitational Waves using Planck, WMAP, and BICEP/Keck Observations through the 2018 Observing Season
• Monodromy in the CMB: Gravity Waves and String Inflation
• The trouble with $H_0$
• Planck evidence for a closed Universe and a possible crisis for cosmology
• The Expansion of the Universe is Faster than Expected
• Early dark energy, the Hubble-parameter tension, and the string axiverse
• On the Hubble constant tension in the SNe Ia Pantheon sample
• Stress Testing $\Lambda$CDM with High-redshift Galaxy Candidates
• Measurements of the E-Mode Polarization and Temperature-E-Mode Correlation of the CMB from SPT-3G 2018 Data
• On the evolution of the Hubble constant with the SNe Ia Pantheon Sample and Baryon Acoustic Oscillations: a feasibility study for GRB-cosmology in 2030
• Arbitrating the $S_8$ discrepancy with growth rate measurements from Redshift-Space Distortions
• Cluster Cepheids with High Precision Gaia Parallaxes, Low Zeropoint Uncertainties, and Hubble Space Telescope Photometry
• The Atacama Cosmology Telescope: Constraints on Pre-Recombination Early Dark Energy
• Constraints on the Hubble constant from Supernova Refsdal's reappearance
• Dark Energy at early times and ACT: a larger Hubble constant without late-time priors
• Hints of Early Dark Energy in Planck, SPT, and ACT data: new physics or systematics?
• The Lyman-alpha forest power spectrum from the XQ-100 Legacy Survey
• Implication of the Hubble tension for the primordial Universe in light of recent cosmological data
• Determining the Hubble Constant without the Sound Horizon: Measurements from Galaxy Surveys
• Towards early dark energy and $n_s$=1 with Planck, ACT and SPT
• Updated constraints from the effective field theory analysis of BOSS power spectrum on Early Dark Energy
• Hybrid cosmological attractors
• Testing H0 in Acoustic Dark Energy Models with Planck and ACT Polarization
• Testing AdS early dark energy with Planck, SPTpol and LSS data
• Towards hybrid inflation with $n_s=1$ in light of Hubble tension and primordial gravitational waves
• Determining the Hubble Constant without the Sound Horizon: A $3.6\%$ Constraint on $H_0$ from Galaxy Surveys, CMB Lensing and Supernovae
• Very Hairy Inflation
• Constraints on Pre-Recombination Early Dark Energy from SPT-3G Public Data
• Determining the Hubble Constant without the Sound Horizon: Perspectives with Future Galaxy Surveys
• Small-scale clumping at recombination and the Hubble tension
• Power-law Inflation Satisfies Penrose's Weyl Curvature Hypothesis

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• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• Negative cosmological constant in the dark energy sector: tests from JWST photometric and spectroscopic observations of high-redshift galaxies
• A double take on early and interacting dark energy from JWST
• Combining pre- and post-recombination new physics to address cosmological tensions: case study with varying electron mass and sign-switching cosmological constant
• Is the Harrison-Zel'dovich spectrum coming back? ACT preference for $n_s\sim 1$ and its discordance with Planck
• Broken blue-tilted inflationary gravitational waves: a joint analysis of NANOGrav 15-year and BICEP/Keck 2018 data
• Inflation, the Hubble Tension and Early Dark Energy: an alternative overview
• Inflationary Potential as seen from Different Angles: Model Compatibility from Multiple CMB Missions
• On the consistency of $\Lambda$CDM with CMB measurements in light of the latest Planck, ACT, and SPT data
• Cosmological constraints on early dark energy from the full shape analysis of eBOSS DR16
• Testing the $n_s-H_0$ scaling relation with Planck-independent CMB data
• Tracking the Multifield Dynamics with Cosmological Data: A Monte Carlo approach
• Reconciling early dark energy with a Harrison-Zeldovich spectrum
• Testing scale-invariant inflation against cosmological data
• Non-oscillating Early Dark Energy and Quintessence from Alpha-Attractors
• Explanation of high redshift luminous galaxies from JWST by early dark energy model
• Can the sound horizon-free measurement of $H_0$ constrain early new physics?
• One Extension to Explain Them All, One Scale-Invariant Spectrum to Test Them All, and in One Model Bind Them
• Gravitational waves in a cyclic Universe: resilience through cycles and vacuum state
• Harrison-Zeldovich attractor: From Planck to ACT results
• Do JWST reionization (optical depth) puzzle, cosmological tensions, and CMB anomalies imply Harrison-Zel'dovich spectrum?