Quantum Chaos for the Unitary Fermi Gas from the Generalized Boltzmann Equations

we study the chaotic behavior of the unitary Fermi gas in both high and low temperature limits by calculating the Quantum Lyapunov exponent defined in terms of the out-of-time-order correlator. We take the method of generalized Boltzmann equations derived from the augmented Keldysh approach. At high temperature, the system is described by weakly interacting fermions with two spin components and in the low temperature limit, the system is a superfluid and can be described by phonon modes. By comparing these to existing results of heat conductivity, we find that D\ll v^2 \tau_L. We argue that this is related to conservation laws for such systems with quasi-particles.