2025 Theory days on Ehrenfest dynamics and beyond

Aim and objectives

Following the tradition of the previous successful meetings that have started in 2009, the Theory Days workshop aims at stimulating constructive discussions, collaborations, and knowledge exchange among a selected group of theoreticians. This year, the 17th edition will be dedicated to “Ehrenfest Dynamics and beyond”.

The coupling of electrons to ionic degrees of freedom is a central issue for the global understanding of dynamics in molecules and clusters. This is especially true in the case of dynamical scenarios far off equilibrium such as those experienced during irradiation processes by a laser or via the interaction with a swift charged projectiles. While short time dynamics may usually be safely analysed overlooking ionic dynamics, the account of the latter cannot be omitted on longer time scales. This is thus essential to properly account for the coupling of electrons to ions during the whole dynamical evolution in order to reach a complete description for example of irradiation scenarios. This is clearly a must go to theory approaches but it is also crucial to link modelling to experimental results which are often attained on time scales much larger than the explored processes themselves.

Usual treatments of electron dynamics couple to ions in an “average way” often loosely quoted “Ehrenfest dynamics”. Ehrenfest dynamics may be sufficient to address some classes of dynamical scenarios but is well known to suffer from potentially severe defects in some other situations, for example when bifurcations take place. These defects are known since long and numerous methods have been developed over the years to overcome (some of) these difficulties. The aim of the workshop is to discuss state of the art of some of these methods developed to overcome limitations of standard Ehrenfest dynamics. Recent developments will be particularly addressed, in particular to the extent that increasing computational power allows more and more ambitious and realistic complete treatment of dynamics.

We plan to gather people from various groups working in this domain, mostly in western Europe. The workshop is intended to be a working forum, thus rather informal. The format will consist in a series of long detailed talks, typically 1 hour (40 mn talk + 10 mn for questions) focusing in particular on ongoing problems and open issues. We thus urge participants to prepare their talks in this spirit. Ultimately a most efficient organization would consist in having a limited number of talks per representative group in order to avoid doublings.

Scientific program and Venue

The meeting will take place from Wednesday November 26th to Friday November 28th. It will be a hybrid event. While on-site attendance allows better exchanges between participants, we will nevertheless leave the possibility of on-line participation. The venue will be in the seminar room of the 3R1 building, see location https://maps.app.goo.gl/3zHVtwu4uvv5VYSS7).