Non-fermi liquids and the Wiedemann-Franz law

This talk will present a general discussion of the ratio of thermal
and electrical conductivities in non-Fermi liquid metals. The
conductivities of non-Fermi liquids are obtained within a
fundamentally different kinematics to Fermi liquids. Among these
strongly interacting non-Fermi liquids we distinguish cases with only
one almost-conserved momentum, and with many patchwise
almost-conserved momenta. We obtain universal expressions for the
ratio of conductivities that violate the Wiedemann-Franz law. We
further discuss the case in which long-lived `cold' quasiparticles, in
general with unconventional scattering rates, coexist with strongly
interacting hot spots, lines or bands. For these cases, we
characterize circumstances under which a linear in temperature
resistivity is and is not compatible with the Wiedemann-Franz law. We
suggest the likely outcome of future transport experiments on CeCoIn5,
YbRh2Si2 and Sr3Ru2O7 at their critical magnetic fields.