WITP Colloquium: Alex Buchel

Mon. Jun. 6 11:00 AM - Mon. Jun. 6 12:20 PM
Location: In Person 3M69 & via Zoom

Alex Buchel, Western University & Perimter Institute

Dynamical fixed points in strongly coupled holographic systems

Typically, an interactive system evolves towards thermal equilibrium, with hydrodynamics representing a universal framework for its late-time dynamics. Classification of the dynamical fixed points (DFPs) of a driven Quantum Field Theory (with time dependent coupling constants, masses, external background fields, etc.) is unknown. We use holographic framework to analyze such fixed points in one example of strongly coupled gauge theory, driven by homogeneous and isotropic expansion of the background metric - equivalently, a late-time dynamics of the corresponding QFT in Friedmann-Lemaitre-Robertson-Walker Universe. We identify DFPs that are perturbatively stable, and those that are perturbatively unstable, computing the spectrum of the quasinormal modes in the corresponding holographic dual. We further demonstrate that a stable DFP can be unstable non-perturbatively, and explain the role of the entanglement entropy density as a  test for a non-perturbative stability. Finally, we demonstrated that a driven evolution might not have a fixed point at all: the entanglement entropy density of a system can grow without bounds.

**NOTE: Attending the talk in-person is only available to those who are regular UofW faculty/staff/students, and/or you've received special permission from the department of Physics.

Zoom for those who can't attend in person:

https://us06web.zoom.us/j/87288391915?pwd=QUZzLzFkSjRXZVNweXg5SXVwVG9KUT09
Meeting ID: 872 8839 1915
Passcode: 704273