
Young Seminar
Organizers: Douglas Lundholm (IHP) & Julien Sabin (Cergy)
Antoine Levitt (ParisDauphine): "The multiconfiguration DiracFock model"
Tuesday 07 May 2013, 14:00  15:00
Room 314
Abstract: We consider the Nbody problem for an atomic or molecular system, in the BornOppenheimer approximation. Since this problem is too big to solve, approximation methods such as the HartreeFock model are routinely used to compute electronic properties of molecules or solids. We will examine a twoway generalization of this model, to the multiconfiguration (several Slater determinants) and relativistic (using the Dirac operator) case.
The HartreeFock model was studied rigorously by LiebSimon (1977) and Lions (1987), the DiracFock model by EstebanSéré (1999), and the multiconfiguration nonrelativistic model by Friesecke (2003) and Lewin (2004). The relativistic multiconfiguration case poses new mathematical issues : because of the properties of the Dirac operator, the equations involving orbitals with small occupation numbers only make sense when the speed of light is sufficiently large. After a presentation of the context and a review of previous works, I will sketch a proof of the existence of "ground states" for the multiconfiguration DiracFock model, in the weakly relativistic regime.