2004ApJ...611...26M

I present a model devoid of nonbaryonic cold dark matter (CDM) that provides an acceptable fit to the Wilkinson Microwave Anisotropy Probe (WMAP) data for the power spectrum of temperature fluctuations in the cosmic background radiation. An a priori prediction of such no-CDM models was a first-to-second peak amplitude ratio A_1:2~2.4. WMAP measures A_1:2=2.34±0.09. The baryon content is the dominant factor in fixing this ratio; no-CDM models that are consistent with the WMAP data are also consistent with constraints on the baryon density from the primordial abundances of ²H, ⁴He, and ⁷Li. However, in order to match the modest width of the acoustic peaks observed by WMAP, a substantial neutrino mass is implied: m_ν~1 eV. Even with such a heavy neutrino, structure is expected to form rapidly under the influence of modified Newtonian dynamics. Consequently, the epoch of reionization should occur earlier than is nominally expected in ΛCDM. This prediction is realized in the polarization signal measured by WMAP. An outstanding test is in the amplitude of the third acoustic peak. Experiments that probe high l appear to favor a third peak that is larger than predicted by the no-CDM model.