Theory HEP Seminar

Out-of-time-order correlators and effective field theory

Felix Haehl

University of British Columbia

In the first part of the talk I will analyze the general structure of out-of-time-order (OTO) correlators, which are expected to play an important role in understanding phenomena such as dissipation, quantum chaos, scrambling etc.. A particular focus will be on the way that unitarity leads to certain redundancies in the path integral description. I will argue that these redundancies can be efficiently understood and encoded as BRST-type symmetries. I will also address further redundancies introduced by the KMS condition in thermal states, and how to organize them efficiently. This opens the path to a systematic analysis of the physics described by thermal OTO n-point functions. In the second part of the talk, I consider the problem of formulating effective field theories of the OTO path integral for near-thermal states. I will argue that the BRST symmetries (and KMS condition) of the microscopic setup lead to a universal supersymmetric structure in the effective description. I show how the control gained by such a symmetry principle can be very useful in understanding, for example, dissipative processes (“information loss”) in systems such as fluids and large black holes.