Multiple Peaks in the Angular Power Spectrum of the Cosmic Microwave Background: Significance and Consequences for Cosmology
P. de Bernardis, P. A. R. Ade, J. J. Bock, J. R. Bond, J. Borrill, A. Boscaleri, K. Coble, C. R. Contaldi, B. P. Crill, G. De Troia, P. Farese, K. Ganga, M. Giacometti, E. Hivon, V. V. Hristov, A. Iacoangeli, A. H. Jaffe, W. C. Jones, A. E. Lange, L. Martinis, S. Masi, P. Mason, P. D. Mauskopf, A. Melchiorri, T. Montroy, C. B. Netterfield, E. Pascale, F. Piacentini, D. Pogosyan, G. Polenta, F. Pongetti, S. Prunet, G. Romeo, J. E. Ruhl, F. Scaramuzzi
TL;DR
BOOMERANG's improved CMB power spectrum reveals three acoustic peaks near $\ell \sim 210, 540, 840$ and two dips near $\ell \sim 420, 750$, supporting the adiabatic inflationary CDM framework. The authors perform model-independent peak/dip measurements and compare them against a 7-parameter cosmological grid using both Bayesian marginalization and likelihood maximization across independent pipelines, obtaining concordant constraints on $\Omega_{tot}$, $\Omega_b h^2$, and $n_s$, with $n_s$ correlated with optical depth $\tau$. They show robust agreement with independent experiments (DASI, MAXIMA) and demonstrate consistency with BBN baryon density. The work also forecasts subsequent peak locations, strengthening the case for a near-flat, baryon-dominated universe and providing a cross-validated methodology for CMB parameter estimation.
Abstract
Three peaks and two dips have been detected in the power spectrum of the cosmic microwave background from the BOOMERANG experiment, at $\ell \sim 210, 540, 840$ and $\ell \sim 420, 750$, respectively. Using model-independent analyses, we find that all five features are statistically significant and we measure their location and amplitude. These are consistent with the adiabatic inflationary model. We also calculate the mean and variance of the peak and dip locations and amplitudes in a large 7-dimensional parameter space of such models, which gives good agreement with the model-independent estimates, and forecast where the next few peaks and dips should be found if the basic paradigm is correct. We test the robustness of our results by comparing Bayesian marginalization techniques on this space with likelihood maximization techniques applied to a second 7-dimensional cosmological parameter space, using an independent computational pipeline, and find excellent agreement: $Ω_{\rm tot} = 1.02^{+0.06}_{-0.05}$ {\it vs.} $1.04 \pm 0.05$, $Ω_b h^2 = 0.022^{+0.004}_{-0.003}$ {\it vs.} $0.019^{+0.005}_{-0.004}$, and $n_s = 0.96^{+0.10}_{-0.09}$ {\it vs.} $0.90 \pm 0.08$. The deviation in primordial spectral index $n_s$ is a consequence of the strong correlation with the optical depth.