Exact deconstruction of the 6D (2,0) theory

The dimensional-deconstruction prescription of Arkani-Hamed, Cohen, Kaplan, Karch and Motl provides a mechanism for recovering the A-type (2,0) theories on T-2, starting from a four-dimensional N = 2 circular-quiver theory. We put this conjecture to the test using two exact-counting arguments: in the decompactification limit, we compare the Higgs-branch Hilbert series of the 4D N = 2 quiver to the "half- BPS" limit of the (2,0) superconformal index. We also compare the full partition function for the 4D quiver on S-4 to the (2,0) partition function on S-4 x T-2. In both cases we find exact agreement. The partition function calculation sets up a dictionary between exact results in 4D and 6D.