AI Article Synopsis
- - The difference in the Hubble parameter values derived from local measurements versus those from the cosmic microwave background (CMB) has led to a deeper investigation of the assumptions behind both methods.
- - The position of the recombination peak in the CMB B-mode power spectrum acts as a new standard ruler, allowing for cross-checks against the acoustic peaks in the CMB temperature power spectrum and helping to address the Hubble tension.
- - Future stage-IV B-mode experiments could achieve a measurement precision better than 2%, which would also help determine the speed of gravitational wave propagation in the early Universe.
Article Abstract
The discrepancy between the Hubble parameter inferred from local measurements and that from the cosmic microwave background (CMB) has motivated careful scrutiny of the assumptions that enter both analyses. Here we point out that the location of the recombination peak in the CMB B-mode power spectrum is determined by the light horizon at the surface of last scatter and thus provides an alternative early-Universe standard ruler. It can thus be used as a cross-check for the standard ruler inferred from the acoustic peaks in the CMB temperature power spectrum and to test various explanations for the Hubble tension. The measurement can potentially be carried out with a precision of ≲2% with stage-IV B-mode experiments. The measurement can also be used to measure the propagation speed of gravitational waves in the early Universe.
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| http://dx.doi.org/10.1103/PhysRevLett.124.041301 | DOI Listing |
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