摘要：Aim.The lack of large-angle correlations in the fluctuations of the cosmic microwave background (CMB) conflicts with predictions of slow-roll inflation. But while probabilities (≲0.24%) for the missing correlations disfavour the conventional picture at ≳3σ, factors not associated with the model itself may be contributing to the tension. Here we aim to show that the absence of large-angle correlations is best explained with the introduction of a non-zero minimum wave numberkminfor the fluctuation power spectrumP(k).Methods.We assumed that quantum fluctuations were generated in the early Universe with a well-defined power spectrumP(k), although with a cut-offkmin≠ 0. We then re-calculated the angular correlation function of the CMB and compared it withPlanckobservations.Results.ThePlanck2013 data rule out a zerokminat a confidence level exceeding 8σ. Whereas purely slow-roll inflation would have stretched all fluctuations beyond the horizon, producing aP(k) withkmin= 0 – and therefore strong correlations at all angles – akmin≠ 0 would signal the presence of a maximum wavelength at the time (tdec) of decoupling. This argues against the basic inflationary paradigm, and perhaps even suggests non-inflationary alternatives, for the origin and growth of perturbations in the early Universe. In at least one competing cosmology, theRh=ctuniverse, the inferredkmincorresponds to the gravitational radius attdec.
关键词：Key wordsencosmic background radiationcosmology: observationscosmology: theoryearly Universeinflationlarge-scale structure of Universe
