Description
Charge can be transported in holography with a finite DC
conductivity via various momentum relaxation mechanisms.
Focusing on relaxation by massless scalars or helical
lattices, I explain how to compute the DC conductivity in
terms of horizon data, and investigate the nature of charge
transport in effective holographic theories, characterized
by at most four scaling exponents. The DC conductivity can
be dominated either by pair creation or momentum
dissipation, and lead to metallic or insulating phases.
Moreover, at low frequencies, the optical conductivity need
not scale covariantly as a function of frequency over
temperature.
The talk will be based on arXiv:1401.5436 and arXiv:1406.6351.
