Hubble constant hunter’s guide

By Lloyd Knox, M. Millea. 2020

316 citations recorded by the source corpus.

Measurements of the Hubble constant and, more generally, measurements of the expansion rate and distances over the interval $0lzl1$ appear to be inconsistent with the predictions of the standard cosmological model ($\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$) given observations of cosmic microwave background temperature and polarization anisotropies. Here we consider a variety of types of departures from $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ that could, in principle, restore concordance among these datasets, and we explain why we find almost all of them unlikely to be successful. We single out the set of solutions that increases the expansion rate in the decade of scale factor expansion just prior to recombination as the least unlikely. These solutions are themselves tightly constrained by their impact on photon diffusion and on the gravitational driving of acoustic oscillations of the modes that begin oscillating during this epoch---modes that project on to angular scales that are very well measured. We point out that a general feature of such solutions is a residual to fits to $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$, like the one observed in Planck power spectra. This residual drives the modestly significant inferences of angular-scale dependence to the matter density and anomalously high lensing power, puzzling aspects of a dataset that is otherwise extremely well fit by $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/3880c21bd5219e630440e59d1d562a22451c100a

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Citations in the corpus

Early dark energy does not restore cosmological concordance (2020, background): “It has been argued (Knox & Millea (2020)) that the proposal “least unlikely to be successful” is an increase in the expansion rate just prior to recombination, which acts to shrink the sound horizon at last scattering.”
New physics in light of the H0 tension: An alternative view (2019, background): “the discussion in [154]).”
Interacting dark energy in the early 2020s: A promising solution to the H0 and cosmic shear tensions (2019, methodology): “t almost attributable) to a statistical uctuation. However, our ndings also reinforce previous results indicating that nding late-time solutions to the H 0 tension is challenging (but not impossible) [13, 49, 75, 278, 279]. We also remind the reader that, within the ˘CDM model, the Planck and BAO/Pa”
The Hubble Constant from Infrared Surface Brightness Fluctuation Distances (2021, background): “A significant discrepancy between the locally measured H0 and the value implied by primordial density fluctuations within the context of ΛCDM may point to physics beyond the standard paradigm (e.g., Planck Collaboration et al. 2020; Poulin et al. 2019; Knox & Millea 2020).”
The Hubble tension in light of the Full-Shape analysis of Large-Scale Structure data (2020, background): “A good review of the possible directions is [87], where it is argued that the class of models “least unlikely to be successful” involves an increase in the expansion H(z) prior to recombination, in order to decrease the sound horizon at recombination.”
Resolving the Hubble tension with new early dark energy (2020, methodology): “[12] L.”
A buyer’s guide to the Hubble constant (2021, background): “The model shows a small residual oscillatory signal in the CMB spectrum versus a standard ΛCDM fit, so if H0 is calculated in ΛCDM in an EDE universe, it is progressively biased lower for higher angular resolution (Knox and Millea 2020).”
Constraining early dark energy with large-scale structure (2020, background): “, [25]; a prototypical model realization goes by the name “early dark energy” (EDE) [26].”
Cosmology Intertwined II: The Hubble Constant Tension (2020, unknown): “[108] L.”
Measurements of the E -mode polarization and temperature- E -mode correlation of the CMB from SPT-3G 2018 data (2021, background): “Hubble tension are difficult to achieve within the ΛCDM model, model extensions may reconcile the discrepancy between high- and low-redshift probes [76].”