The local SYK model and its triple scaling limit

Abstract

We study a model of fermions with random couplings similar to conventional SYK with $N$ number of flavours of fermions, at large $N$. Unlike the conventional SYK model, which has all-to-all couplings, the model we study, which we call local SYK, has a much less number of random couplings, just $N$ in number and with only local interactions. It is shown that there exists a limit in which the local SYK model can be solved using the chord diagram techniques, analogous to the double-scaled limit of conventional SYK. This limit corresponds to taking the size of the fermion coupling terms, $q$, to scale linearly with $N$. A further triple scaling limit is taken to analyze the low energy limit and it is shown that the OTOCs saturate the chaos bound, paralleling the analysis in the conventional SYK.