[Landau ITP Seminars] Friday 02.12.2022

[Serge Krashakov]

Уважаемые коллеги!

Напоминаю, что в 16:00 состоится коллоквиум, на котором будет заслушан 
доклад:

A. Polkovnikov (Boston University, USA)


    Understanding quantum and classical chaos in Hamiltonian systems
    through adiabatic transformations

Chaos is synonymous to unpredictability. In the case of classical 
systems this unpredictability is expressed through exponential 
sensitivity of trajectories to tiny fluctuations of the Hamiltonian or 
to the initial conditions. It is well known that chaos is closely 
related to ergodicity or emergence of statistical mechanics at long 
times, but the precise relations between them are still debated. In 
quantum systems the situation is even more controversial with 
trajectories being ill-defined. A standard approach to defining quantum 
chaos is through emergence of the random matrix theory. However, as I 
will argue, this approach is rather related to the eigenstate 
thermalization hypothesis and ergodicity than to chaps. In this talk I 
will suggest that one can use fidelity susceptibility of equivalently 
geometric tensor and quantum Fisher information as a definition of 
chaos, which applies both to quantum and classical systems and which is 
related to long time tails of the auto-correlation functions of local 
perturbations. Through this approach we can establish of existence of 
the intermediate chaotic but non-ergodic regime separating integrable 
and ergodic phases, which have maximally sensitive eigenstates. I will 
discuss how this measure is also closely related to recently proposed 
definition of chaos through the Krylov complexity or the operator growth 
and that there is very interesting and still unexplained duality between 
short and long time behavior of chaotic and integrable systems As a 
specific example of this approach I will apply these ideas to 
interacting disordered systems and show that (many-body) localization is 
unstable in thermodynamic limit irrespective of the disorder strength.


ID и пароль онлайн-трансляций в Zoom те же, что и для предыдущих 
трансляций докладов на Ученом совете:
https://zoom.us/j/96899364518?pwd=MzBsR2lYT0lYL2x2b1oyNU9LeWlWUT09
Meeting ID: 968 9936 4518
Пароль: 250319
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