Wrapped $M5$-branes and complex saddle points

We study the effects of the introduction of a $\vartheta$ term in minimal gauged supergravity in four dimensions. We show why this term is not present in supergravity duals of field theories arising on wrapped $M2$-branes, but is there in the case of $M5$-branes wrapping hyperbolic manifolds $\Sigma_3$, and compute the higher-derivative corrections. Having proved that the on-shell supergravity action of any supersymmetric solution can be expressed in terms of data from the fixed points of a Killing vector, we show that it is proportional to a complex topological invariant of $\Sigma_3$. This is consistent with the characteristics of the dual three-dimensional $\mathcal{N}=2$ SCFT predicted by the $3d$-$3d$ correspondence, and we match the large $N$ limit of its partition functions in the known cases.