An obstacle to sub-AdS holography for SYK-like models

Understand

We argue that "stringy" effects in a putative gravity-dual picture for SYK-like models are related to the branching time, a kinetic coefficient defined in terms of the retarded kernel.

• A bound on the branching time is established assuming that the leading diagrams are ladders with thin rungs.
• Thus, such models are unlikely candidates for sub-AdS holography.
• In the weak coupling limit, we derive a relation between the branching time, the Lyapunov exponent, and the quasiparticle lifetime using two different approximations.