English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT) haverecently provided new, very precise measurements of the cosmic microwavebackground (CMB) anisotropy damping tail. The values of the cosmologicalparameters inferred from these measurements, while broadly consistent with theexpectations of the standard cosmological model, are providing interestingpossible indications for new physics that are definitely worth ofinvestigation. The ACT results, while compatible with the standard expectationof three neutrino families, indicate a level of CMB lensing, parametrized bythe lensing amplitude parameter A_L, that is about 70% higher than expected. Ifnot a systematic, this anomalous lensing amplitude could be produced bymodifications of general relativity or coupled dark energy. Vice-versa, the SPTexperiment, while compatible with a standard level of CMB lensing, prefers anexcess of dark radiation, parametrized by the effective number of relativisticdegrees of freedom N_eff. Here we perform a new analysis of these experimentsallowing simultaneous variations in both these, non-standard, parameters. Wealso combine these experiments, for the first time in the literature, with therecent 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=3.23\pm0.47,A_L=1.65\pm0.33 at 68% c.l., while for SPT we have N_eff=3.76\pm0.34,A_L=0.81\pm0.12 at 68% c.l.. In particular, the A_L estimates from the twoexperiments, even when a variation in N_eff is allowed, are in tension at morethan 95% c.l..

Tickling the CMB damping tail: scrutinizing the tension between the ACT and SPT experiments