Insulators close to the metal insulator transition exhibit interesting collective electronic phenomena which are still rather poorly understood.   A prominent feature in such systems is the purely electronic nature of activated transport apparent in experiments, which is inconsistent with the theory of phonon-assisted hopping conduction and thus has remained an unexplained puzzle for decades.  The situation became even less clear when recently theories of many body localization predicted a metal insulator transition at finite temperature for interacting electrons that are decoupled from phonons.
In this talk I will address this problem for Anderson insulators with a single-particle localization length much larger than the mean distance between electrons.  Under these circumstances Coulomb interactions drive the electrons into a strongly correlated quantum glass phase with non-trivial collective behavior.  I will show that a typical metastable state exhibits a gapless spectrum of collective excitations which act as a bath with which individual electrons can exchange energy. In 2D systems,  this results in a hopping transport mechanism with a nearly universal pre-exponential factor of order e2/h.  This is in good agreement with many recent experiments.