Are We Entering a Paradigm Shift for Dark Matter?

Abstract

While the LCDM framework has been incredibly successful for modern cosmology, it requires the admission of two mysterious substances as a part of the paradigm, dark energy and dark matter. Although this framework adequately explains most of the large-scale properties of the Universe (i.e., existence and structure of the CMB, the large-scale structure of galaxies, the abundances of light elements and the accelerating expansion), it has failed to make significant predictions on smaller scale features such as the kinematics of galaxies and their formation. In particular, the rotation curves of disk galaxies (the original observational discovery of dark matter) are better represented by non-Newtonian models of gravity that challenge our understanding of motion in the low acceleration realm (much as general relativity provided an extension of gravity into the high acceleration realm e.g., blackholes). The tension between current cold dark matter scenarios and proposed new formulations of gravity in the low energy regime suggests an upcoming paradigm shift in cosmology. And, if history is a guide, observations will lead the way.