  By employing the holographic operator mixing technique to deal with coupled
perturbations in the gauge/gravity duality, I numerically compute the real and
imaginary parts of the diagonal and Hall AC conductivities in a strongly
coupled quantum field theory dual to a bulk condensate of magnetic monopoles.
The results obtained show that a conclusion previously derived in the
literature, namely, the vanishing of holographic DC conductivities in
3-dimensional strongly coupled quantum field theories dual to a 4-dimensional
bulk magnetic monopole condensate, also applies to the calculation of diagonal
and Hall conductivities in the presence of a topological $\theta$-term.
Therefore, the condensation of magnetic monopoles in the bulk is suggested as a
rather general and robust mechanism to generate dual strongly coupled quantum
field theories with zero DC conductivities. The interplay between frequency,
$\theta$-angle and the characteristic mass scale of the monopole condensate on
the results for the conductivities is also investigated.
