Chaos exponents of SYK traversable wormholes

Understand

In this paper we study the chaos exponent, the exponential growth rate of the out-of-time-ordered four point functions, in a two coupled SYK models which exhibits a first order phase transition between the high temperature black hole phase and the low temperature gapped phase interpreted as a traversable wormhole.

• We see that as the temperature decreases the chaos exponent exhibits a discontinuous fall-off from the value of order the universal bound $2\pi/\beta$ at the critical temperature of the phase transition, which is consistent with the expected relation between black holes and strong chaos.
• Interestingly, the chaos exponent is small but non-zero even in the wormhole phase.
• This is surprising but consistent with the observation on the decay rate of the two point function [arXiv:2003.03916], and we found the chaos exponent and the decay rate indeed obey the same temperature dependence in this regime.