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Register a new userQuantifying the global parameter tensions between ACT, SPT and Planck
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The overall cosmological parameter tension between the Atacama Cosmology Telescope 2020 (ACT) and Planck 2018 data within the concordance cosmological model is quantified using the suspiciousness statistic to be 2.6$sigma$. Between ACT and the South Pole Telescope (SPT) we find a tension of 2.4$sigma$, and 2.8$sigma$ between ACT and Planck+SPT combined. While it is unclear whether the tension is caused by statistical fluctuations, systematic effects or new physics, caution should be exercised in combining these cosmic microwave background datasets in the context of the $Lambda$CDM standard model of the universe.
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We investigate correlations induced by gravitational lensing on simulated cosmic microwave background data of experiments with an incomplete sky coverage and their effect on inferences from the South Pole Telescope data. These correlations agree well with the theoretical expectations, given by the sum of super-sample and intra-sample lensing terms, with only a typically negligible $sim$ 5% discrepancy in the amplitude of the super-sample lensing effect. Including these effects we find that lensing constraints are in $3.0sigma$ or $2.1sigma$ tension between the SPT polarization measurements and Planck temperature or lensing reconstruction constraints respectively. If the lensing-induced covariance effects are neglected, the significance of these tensions increases to $3.5sigma$ or $2.5sigma$. Using the standard scaling parameter $A_L$ substantially underestimates the significance of the tension once other parameters are marginalized over. By parameterizing the super-sample lensing through the mean convergence in the SPT footprint, we find a hint of underdensity in the SPT region. We also constrain extra sharpening of the CMB acoustic peaks due to missing smoothing of the peaks by super-sample lenses at a level that is much smaller than the lens sample variance. Finally, we extend the usual shift in the means statistic for evaluating tensions to non-Gaussian posteriors, generalize an approach to extract correlation modes from noisy simulated covariance matrices, and present a treatment of correlation modes not as data covariances but as auxiliary model parameters.
The Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT) have recently provided new, very precise measurements of the cosmic microwave background (CMB) anisotropy damping tail. The values of the cosmological parameters inferred from these measurements, while broadly consistent with the expectations of the standard cosmological model, are providing interesting possible indications for new physics that are definitely worth of investigation. The ACT results, while compatible with the standard expectation of three neutrino families, indicate a level of CMB lensing, parametrized by the lensing amplitude parameter A_L, that is about 70% higher than expected. If not a systematic, this anomalous lensing amplitude could be produced by modifications of general relativity or coupled dark energy. Vice-versa, the SPT experiment, while compatible with a standard level of CMB lensing, prefers an excess of dark radiation, parametrized by the effective number of relativistic degrees of freedom N_eff. Here we perform a new analysis of these experiments allowing simultaneous variations in both these, non-standard, parameters. We also combine these experiments, for the first time in the literature, with the recent WMAP9 data, one at a time. Including the Hubble Space Telescope (HST) prior on the Hubble constant and information from baryon acoustic oscillations (BAO) surveys provides the following constraints from ACT: N_eff=3.23pm0.47, A_L=1.65pm0.33 at 68% c.l., while for SPT we have N_eff=3.76pm0.34, A_L=0.81pm0.12 at 68% c.l.. In particular, the A_L estimates from the two experiments, even when a variation in N_eff is allowed, are in tension at more than 95% c.l..
Primordial magnetic fields can change the recombination history of the universe by inducing clumping in the baryon density at small scales. They were recently proposed as a candidate model to relieve the Hubble tension. We investigate the consistency of the constraints on a clumping factor parameter $b$ in a simplistic model, using the latest CMB data from Planck, ACT DR4 and SPT-3G 2018. For the combined CMB data alone, we find no evidence for clumping being different from zero, though when adding a prior on $H_0$ based on the latest distance-ladder analysis of the SH0ES team, we report a weak detection of $b$. Our analysis of simulated datasets shows that ACT DR4 has more constraining power with respect to SPT-3G 2018 due to the degeneracy breaking power of the TT band powers (not included in SPT). Simulations also suggest that the TE,EE power spectra of the two datasets should have the same constraining power. However, the ACT DR4 TE,EE constraint is tighter than expectations, while the SPT-3G 2018 one is looser. While this is compatible with statistical fluctuations, we explore systematic effects which may account for such deviations. Overall, the ACT results are only marginally consistent with Planck or SPT-3G, at the $2-3sigma$ level within $Lambda$CDM+$b$ and $Lambda$CDM, while Planck and SPT-3G are in good agreement. Combining the CMB data together with BAO and SNIa provides an upper limit of b<0.4 at 95% c.l. (b<0.5 without ACT). Adding a SH0ES-based prior on the Hubble constant gives $b = 0.31^{+0.11}_{-0.15}$ and $H_0=69.28 pm 0.56$ km/s/Mpc ($b = 0.41^{+0.14}_{-018}$ and $H_0=69.70 pm 0.63$ km/s/Mpc without ACT). Finally, we forecast constraints on $b$ for the full SPT-3G survey, Simons Observatory, and CMB-S4, finding improvements by factors of 1.5 (2.7 with Planck), 5.9 and 7.8, respectively, over Planck alone.
The Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT) have recently provided new and precise measurements of the Cosmic Microwave Background anisotropy damping tail. This region of the CMB angular spectra, thanks to the angular distortions produced by gravitational lensing, can probe the growth of matter perturbations and provide a test for general relativity. Here we make use of the ACT and SPT power spectrum measurements (combined with the recent WMAP9 data) to constrain f(R) gravity theories. Adopting a parametrized approach, we obtain an upper limit on the lengthscale of the theory of B_0 < 0.86 at 95% c.l. from ACT, while we get a significantly stronger bound from SPT with B_0 < 0.14 at 95% c.l..
We apply a recently developed method to directly measure the gravitational lensing power spectrum from CMB power spectra to the Planck satellite data. This method allows us to analyze the tension between the temperature power spectrum and lens reconstruction in a model independent way. Even when allowing for arbitrary variations in the lensing power spectrum, the tension remains at the 2.4$sigma$ level. By separating the lensing and unlensed high redshift information in the CMB power spectra, we also show that under $Lambda$CDM the two are in tension at a similar level whereas the unlensed information is consistent with lensing reconstruction. These anomalies are driven by the smoother acoustic peaks relative to $Lambda$CDM at $ell sim 1250 - 1500$. Both tensions relax slightly when polarization data are considered. This technique also isolates the one aspect of the lensing power spectrum that the Planck CMB power spectra currently constrain and can be straightforwardly generalized to future data when CMB power spectra constrain multiple aspects of lensing which are themselves correlated with lensing reconstruction.
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