Subleading Microstate Counting in the Dual to Massive Type IIA

We study the topologically twisted index of a certain Chern-Simons matter theory with $SU(N)$ level $k$ gauge group on a genus $g$ Riemann surface times a circle. For this theory it is known that the logarithm of the topologically twisted index grows as $N^{5/3}$ and that it matches the Bekenstein-Hawking entropy of certain magnetically charged asymptotically $AdS_4\times S^6$ black holes in massive type IIA supergravity. Through a combination of numerical and analytical techniques we study the subleading in $N$ structure. We demonstrate precise analytic cancellation of terms of orders $N\log\,N$ and $N^{1/3}\log N$ and show numerical cancellation for terms of order $N$. As a result, the first subleading correction is of order $N^{2/3}$. Furthermore, we provide evidence for the presence of a term of the form $(g-1)(7/18) \log \,N$ which constitutes a microscopic prediction for the one-loop contribution coming from the massless gravitational degrees of freedom in the massive IIA black hole.