The chaotic behaviour of classical non-linear systems is an ubiquitous effect which refers to the unpredictability of their complex dynamics, a phenomenon known as the butterfly effect. 

In mathematical terms this concept is characterized by the so-called Lyapunov exponent, a quantity which expresses the rate at which trajectories which start from close-by initial conditions (position and velocity), diverge with time. In quantum mechanics it is difficult to find good diagnostics of chaos and this question has been intensively debated since the beginnings of quantum mechanics. Recently, groundbreaking results from high energy physics [1] showed that quantum mechanics imposes a strict bound on the Lyapunov exponent.

This novel effect has motivated enormous interest over different fields, leaving, however, several outstanding open questions. In our work [2] we show that this bound can be regarded as a consequence of the quantum fluctuation-dissipation theorem, a fundamental result of statistical mechanics which connects the linear response to a perturbation with the equilibrium thermal fluctuations. These findings establish a direct connection between quantum chaos and other thermodynamic properties. They could give rise to new applications to different problems. 

In mathematical terms this concept is characterized by the so-called Lyapunov exponent, a quantity which expresses the rate at which trajectories which start from close-by initial conditions (position and velocity), diverge with time. In quantum mechanics it is difficult to find good diagnostics of chaos and this question has been intensively debated since the beginnings of quantum mechanics. Recently, groundbreaking results from high energy physics [1] showed that quantum mechanics imposes a strict bound on the Lyapunov exponent. This novel effect has motivated enormous interest over different fields, leaving, however, several outstanding open questions. In our work [2] we show that this bound can be regarded as a consequence of the quantum fluctuation-dissipation theorem, a fundamental result of statistical mechanics which connects the linear response to a perturbation with the equilibrium thermal fluctuations. These findings establish a direct connection between quantum chaos and other thermodynamic properties. They could give rise to new applications to different problems.

[1] J. Maldacena, S. H. Shenker and D. Stanford, Journal of High Energy Physics 2016(8) (2016).
[2] S. Pappalardi, L. Foini and J. Kurchan, SciPost Phys. 12, 130 (2022).

The microscopic description of black holes has been a challenge for more that forty years. 

There are now quite a number of promising approaches to solving this problem and the primary goal of this conference and workshop is to bring together experts in these areas to identify synergies, engage in constructive criticism and resolve apparent conflicts.  A significant focus will be the dynamics of black-hole microstructure: how infalling matter is scrambled and how information is recovered.

The conference will be held online-only on Monday 6^th of June (which is a public holiday in France) and then in person at the IPhT, CEA-Saclay from Tuesday 7^th to Friday 10^th of June. Every day of the conference will also be broadcast. Registration at the website.

The conference will be followed by a workshop at the IPhT on particular and more technical issues associated with black-hole microstructure.

Organizers: Iosif Bena (IPhT), Andrea Puhm (CNRS, CPHT)  and Nick Warner (IPhT, USC)

https://indico.in2p3.fr/event/26435/

The next colloquium Rencontres de l'IPhT conference will be held in Autrans (Vercors) from 23 to 25 May. It will consist of conferences and lectures concerning both the major fields of research in theoretical physics and supporting activities.

The main themes of physics will be:
- Mathematical physics: group A
- Cosmology, particles and nuclei: group B
- Statistical physics - condensed matter: group C

Main goals:
- To share knowledge on scientific topics and strengthening cohesion within the Institute.
- To bring together all of the Institute's collaborators in order to discuss common subjects and activities and to strengthen interactions between members of the different teams, including support.
- To unite the teams around a common project.

See you soon in Autrans!