DOES COSMOLOGICAL STRUCTURE FORMATION REQUIRE DARK ENERGY?

Precision measurements of anisotropies in the cosmic microwave background and of the clustering of large-scale structure have supposedly established that the universe is presently dominated by "dark energy" which has negative pressure and behaves similarly to a cosmological constant. This is based on the assumption that the primordial density perturbation has a nearly scale-invariant power-law spectrum and that the dark matter consists of "cold" particles. However there are theoretical and observational indications that the spectrum is not scale-free and it is known that sub-eV mass neutrinos contribute a small component of hot dark matter. This would be sufficient to fit the same observational data without requiring any dark energy. © EAS, EDP Sciences 2009