Tree tensor network study of out-of-time-order correlators on a sparse graph

The SYK model, which consists of Majorana fermions with random few-fermion all-to-all interactions, is a paradigmatic model of a "fast scrambler". Recent work (Bentsen, Gu, and Lucas: PNAS 116, 6689) argued that all-to-all connectivity is not necessary: rather, interactions on a sparse connectivity graph are sufficient. Because many such graphs are locally treelike, they are amenable to treatment with tree tensor networks. In this talk I will describes a study of out-of-time-order correlators using tree tensor networks; I will also comment on some methodological subtleties.