Signals from the early Universe: a comprehensive search for primordial features in Planck CMB datasets

arXiv astro-phr90May 28, 2026, 05:07 PMInternational

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Excerpt

We investigate the presence of primordial oscillatory features in measurements of CMB anisotropies through a systematic comparison of phenomenological templates. Building upon previous searches for primordial features using Planck data, we compare the full PR3 legacy release with the PR4 (NPIPE) processing to assess how the results depend on the choice of CMB maps and likelihood framework. To maximise our sensitivity to rapidly varying oscillatory signals, we employ unbinned likelihoods. We find that several previously reported indications of oscillatory structure persist across different analyses, although none attains global statistical significance. Furthermore, some anomalies reported in earlier studies are substantially reduced when updated to the new versions of the CamSpec likelihood using Planck PR4 products. For all templates considered, we identify a small number of frequencies in the range $ω\sim 10-100$ that improve the fit to the CMB data by up to $Δχ^2 \simeq -10$ to $-15$ relative to the featureless reference model. However, this improvement is not supported by a Bayesian model comparison. The inclusion of three or four additional parameters can reduces the overall p

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