Ramanujan Auditorium

Many-body chaos and dynamical transitions: Classical to quantum and back again

Sumilan Banerjee

Indian Institute of Science

Chaos is an important characterization of classical dynamical systems. However, in
recent years, a quantum Lyapunov exponent, and a butterfly velocity for ballistic
spread of local perturbation, computed from the so-called out-of-time-order commutator
(OTOC) have emerged as important measures for chaos and thermalization in interacting
quantum many-body systems having some well-defined semiclassical limit. In the first
part of the talk, I will describe curious interplay of chaos, quantum fluctuations, symmetry
breaking and complex dynamics across dynamical transition in a quantum spin glass
model. I will discuss the implications of the results in the classical limit of the model
which describes dynamics in supercooled liquid in structural glasses. In the second part of
the talk, I will discuss a surprising noise-induced many-body chaotic to non-chaotic
transition in the classical stochastic Langevin dynamics of interacting integrable and non-
integrable systems.