Separate constraints on early and late cosmology

Since the public release of Planck data, several attempts have been made to explain the observed small tensions with other data sets, most of them involving an extension of the Lambda cold dark matter (Lambda CDM) model. We try here an alternative approach to the data analysis, based on separating the constraints coming from the different epochs in cosmology, in order to assess which part of the standard model generates the tension with the data. To this end, we perform a particular analysis of Planck data probing only the early cosmological evolution, until the time of photon decoupling. Then, we utilize this result to see if the Lambda CDM model can fit all observational constraints probing only the late cosmological background evolution, discarding any information concerning the late perturbation evolution. We find that all tensions between the data sets are removed, suggesting that our standard assumptions on the perturbed late-time history, as well as on reionization, could sufficiently bias our parameter extraction and be the source of the alleged tensions.