# CQD Special Seminar

### 16. May 2019 14:15

Seminarraum, Institut für Theoretische Physik, Philosophenweg 19### Quantum Chaos, hydrodynamics and black hole scrambling

**Professor Koenraad Schalm**

Institute Lorentz for Theoretical Physics, Leiden University

For perturbative scalar field theories, the late-time-limit of the out-of-time-ordered correlation function that measures (quantum) chaos is shown to be equal to a Boltzmann-type kinetic equation that measures the total gross (instead of net) particle exchange between phase space cells, weighted by a function of energy. This derivation gives a concrete form to numerous attempts to derive chaotic many-body dynamics from ad hoc kinetic equations. As in conventional Boltzmann transport, which follows from the dynamics of the net particle number density exchange, the kernel of this kinetic integral equation is also set by the 2-to-2 scattering rate. This provides a mathematically precise statement of the known fact that in dilute weakly coupled gases late-time transport and early-time scrambling (or ergodicity) are controlled by the same physics.

Surprisingly infinitely strongly coupled, large-Nc theories with a holographic dual also possess this relation between early- and late-time physics. The gravitational shock wave computation used to extract the scrambling rate in strongly coupled quantum theories with a holographic dual is directly related to probing the system's hydrodynamic sound modes. At a special point along the sound dispersion relation curve, the residue of the retarded longitudinal stress-energy tensor two-point function vanishes. This pole-skipping point encodes the Lyapunov exponent of quantum chaos.

Dipolar quantum gases: From rotons to supersolids to vortices

*Dr. Manfred Johann Mark, Institut für Experimentalphysik, Universität Innsbruck*, INF 227, Hörsaal 1