one is left with a topological twist of the $\mathcal{N}=4$ theory. This was explored in detail in [@Benini:2013cda; @Benini:2012cz].

We assume that in the IR the effective two-dimensional theory is conformal. Since it preserves $(0,2)$ supersymmetry, we can leverage anomalies to calculate the left and right central charges. The calculation proceeds as in [@Benini:2013cda]. The two-dimensional theory has two Abelian global symmetries: the $R$-symmetry of the LS fixed point given by the generator as well as the $U(1)_F$ subgroup of the $SU(2)_F$ flavor symmetry with the generator . The charges of the fermions under these two Abelian symmetries are given in Table \[table:two\]. The background gauge field is along the generator and has flux proportional to the volume form of the Riemann surface.

The two-dimensional superconformal $R$-symmetry is some linear combination of the Abelian global symmetries of the four-dimensional LS theory $$\label{Ttr}
T_{\rm tr} = \epsilon~ T_F + T_R^{}\;.$$ The real parameter $\epsilon$ is yet undetermined and will be fixed by applying the $c$-extremization procedure [@Benini:2012cz; @Benini:2013cda].[^4] To this end we have to calculate the right-moving trial central charge, $c_r^{\rm tr}(\epsilon)$.

The global symmetries of the two-dimensional theory are anomalous since there are massless chiral fermions. The number of these 