On the consistency of $Λ$CDM with CMB measurements in light of the latest Planck, ACT, and SPT data

Abstract

Using Gaussian Processes we perform a thorough, non-parametric consistency test of the ΛCDM model when confronted with state-of-the-art TT, TE and EE measurements of the anisotropies in the Cosmic Microwave Background by Planck, ACT, and SPT collaborations. We find no statistically significant deviation from ΛCDM's best fit predictions when looking for signatures in the residuals. The results of SPT are in good agreement with the ΛCDM best fit predictions to Planck data, while the results of ACT are only marginally consistent. Interestingly, the slight disagreement between Planck/SPT and ACT is mainly visible in the residuals of the TT spectrum, the latter favoring a scale-invariant tilt 𝑛 𝑠 1, consistent with previous findings using parametric analyses. We also report some features in the EE measurements captured both by ACT and SPT which could be hinting towards a common physical origin, or unknown systematics in the data. Finally, we test the internal consistency of the Planck data alone by studying the high and low-ℓ ranges separately, finding no discrepancy between small and large angular scales. Apart from the mentioned mild inconsistencies in TT and EE, our results show the overall agreement between the various ground and space-based CMB experiments with the standard model of cosmology.

Is the Harrison-Zel’dovich spectrum coming back? ACT preference forns∼ 1 and its discordance with Planck

“…Consequently, also the lensing amplitude aligns with the expected values in the CDM model. Nonetheless, ACT and SPT data in turn show other mild yet rele v ant de viations from the CDM scenario (Di Valentino et al 2022 ;Calder ón et al 2023 ;Di Valentino et al 2023 ), including a ∼2.7 σ discrepancy in the scalar spectral index n s between Planck ( n s = 0.9649 ± 0.0044) and ACT ( n s = 1.008 ± 0.015) that represents a new potential challenge for inflationary cosmology. As with the other tensions mentioned previously, this n s discrepancy could result from a statistical fluctuation, to a (yet unknown) systematic effect in the ACT or Planck data, or a departure from the theoretical CDM framework by assuming canonical inflation as the dominant mechanism for producing the perturbations in the early universe.…”