Abstract: We analyze the large N limit of adjoint QCD, an SU(N) gauge theory with Nf flavors of massless adjoint Majorana fermions, compactified on S3 × S1. We focus on the weakly-coupled confining small-S3 regime. If the fermions are given periodic boundary conditions on S1, we show that there are large cancellations between bosonic and fermionic contributions to the twisted partition function. These cancellations follow a pattern previously seen in the context of misaligned supersymmetry, and lead to the absence of Hagedorn instabilities for any S1 size L, even though the bosonic and fermionic densities of states both have Hagedorn growth. Adjoint QCD stays in the confining phase for any L ∼ N0, explaining how it is able to enjoy large N volume independence for any L. The large N boson-fermion cancellations take place in a setting where adjoint QCD is manifestly non-supersymmetric at any finite N, and are consistent with the recent conjecture that adjoint QCD has emergent fermionic symmetries in the large N limit.
- 1/N Expansion