Revisiting the classifications of 6d SCFTs and LSTs
Journal of High Energy Physics
Gauge-theoretic anomaly cancellation predicts the existence of many 6d SCFTs and little string theories (LSTs) that have not been given a string theory construction so far. In this paper, we provide an explicit construction of all such "missing" 6d SCFTs and LSTs by using the frozen phase of F-theory. We conjecture that the full set of 6d SCFTs and LSTs is obtained by combining the set of theories constructed in this paper with the set of theories that have been constructed in earlier
... n earlier literature using the unfrozen phase of F-theory. Along the way, we demonstrate that there exist SCFTs that do not descend from LSTs via an RG flow. We start in section 2.1 by listing down all the sub-quivers appearing in  but not admitting a construction in the unfrozen phase of F-theory. We then list down all the possible LSTs and SCFTs containing these sub-quivers 4 in sections 2.2 and 2.3 respectively. In compiling 2 See  for initial work on Hanany-Witten-like brane constructions of six-dimensional theories. 3 We emphasize that our list also includes those theories that contain non-gauge-theoretic factors like E-string and N = (2, 0) theory. This is unlike  where the discussion was entirely restricted to gauge theories. 4 We slightly enlarge the extent of the classification of  by allowing some non-gauge-theoretic factors to appear in the low energy theory on the tensor branch in the form of formal gauge algebras sp(0) and su(1).