The smoothing effect of lensing to the CMB temperature power spectrum is, to some extent, degenerate with oscillatory modulations of the primordial power spectrum, in particular if the frequency is close to that of the acoustic peaks. We consider the possibility that the lensing anomaly reported by the latest Planck 2018 results may be hinting at an oscillatory modulation generated by a massive scalar field during an alternative scenario to inflation or by a sharp feature during inflation. We use the full TTTEEE+low E CMB likelihood from Planck to derive constraints on these two types of models. We obtain that in both cases the AL anomaly is mildly reduced to less than 2σ. Moreover, we find that the oscillatory modulation generated during an alternative scenario presents the lowest value of χ2, with Δχ2=13 compared to ΛCDM. Furthermore, the Akaike Information Criterion suggests that such an oscillation constitutes an attractive candidate since it has a value ΔAIC=5 with respect to ΛCDM, comparable to the AL parameter. Interestingly, the matter bounce and radiation bounce scenarios are compatible with our results. We discuss how these models of oscillatory features can be tested with future observations.

G. Domènech, X. Chen, M. Kamionkowski, A. Loeb, “Planck residuals anomaly as a fingerprint of alternative scenarios to inflation”, JCAP 10, 005 (2020).


Related to Project: B01