  We study transport in three dimensional Weyl semimetals with N isotropic Weyl
nodes in the presence of Coulomb interactions or disorder at temperature T. In
the interacting clean limit, we determine the conductivity by solving a quantum
Boltzmann equation within a `leading log' approximation and find it to be
proportional to T, upto logarithmic factors arising from the flow of couplings.
In the noninteracting disordered case, we compute the finite-frequency Kubo
conductivity and show that it exhibits distinct behaviors for omega << T and
omega >> T: in the former regime we recover the results of a previous analysis,
of a finite conductivity and a Drude width that vanishes as NT^2; in the
latter, we find a conductivity that vanishes linearly with omega whose leading
contribution as T -> 0 is the same as that of the clean, non-interacting system
sigma(omega, T=0) = N(e^2/12h)(|omega|/v_F). We compare our results to
experimental data on Y2Ir2O7 and also comment on the possible relevance to
recent transport data on Eu2Ir2O7.
