Electrical transport properties near an electronic Ising-nematic quantum critical point in two dimensions are of both theoretical and experimental interest. In this work, we derive a kinetic equation valid in a broad regime near the quantum critical point using the memory matrix approach. The formalism is applied to study the effect of the critical fluctuations on the dc resistivity through different scattering mechanisms, including umklapp, impurity scattering, and electron-hole scattering in a compensated metal. We show that electrical transport in the quantum critical regime exhibits a rich behavior that depends sensitively on the scattering mechanism and the band structure. In the case of a single large Fermi surface, the resistivity due to umklapp scattering crosses over from $\ensuremath{\rho}\ensuremath{\sim}{T}^{2}$ at low temperature to sublinear at high temperature. The crossover temperature scales as
q03, where
q0 is the minimal wave vector for umklapp scattering. Impurity scattering leads to $\ensuremath{\rho}\ensuremath{-}{\ensuremath{\rho}}_{0}\ensuremath{\sim}{T}^{\ensuremath{\alpha}}$ (${\ensuremath{\rho}}_{0}$ being the residual resistivity), where $\ensuremath{\alpha}$ is either larger than 2 if there is only a single Fermi sheet present, or
4/3 in the case of multiple Fermi sheets. Finally, in a perfectly compensated metal with an equal density of electrons and holes, the low-temperature behavior depends strongly on the structure of ``cold spots'' on the Fermi surface, where the coupling between the quasiparticles and order parameter fluctuations vanishes by symmetry. In particular, for a system where cold spots are present on some (but not all) Fermi sheets, $\ensuremath{\rho}\ensuremath{\sim}{T}^{5/3}$. At higher temperatures, there is a broad crossover regime where $\ensuremath{\rho}$ either saturates or $\ensuremath{\rho}\ensuremath{\sim}T$, depending on microscopic details. We discuss these results in the context of recent quantum Monte Carlo simulations of a metallic Ising nematic critical point, and experiments in certain iron-based superconductors.
We show that if the excitations which become gapless at a quantum critical point also carry the electrical current, then a resistivity linear in temperature, as is observed in the copper-oxide high-temperature superconductors, obtains only if the dynamical exponent z satisfies the unphysical constraint, z < 0. At fault here is the universal scaling hypothesis that, at a continuous phase transition, the only relevant length scale is the correlation length. Consequently, either the electrical current in the normal state of the cuprates is carried by degrees of freedom which do not undergo a quantum phase transition, or quantum critical scenarios must forgo this basic scaling hypothesis and demand that more than a single-correlation length scale is necessary to model transport in the cuprates.