1 Tribute to Daniel Gogny 08/12/15 Detours may (sometime) be the best way, views from former physicists D. Iracane & P. Chaix, CEA/Saclay

2 Tribute to Daniel Gogny 08/12/15 Being a disciple of Daniel Gogny approach In 1982, Daniel Gogny was searching in QFT some rationale for his successful Force Later in the 80s, the Strategic Defense US initiative raised questions about the Free Electron Laser operational capacities Fundamental approaches within an “applied science organization”: Questions arising from operational considerations. Work for a deep understanding, in an open, free and rigorous approach. Push (when possible) up to the end of the story, whatever the detours, to get robust results. Fun and excitement!

3 Tribute to Daniel Gogny 08/12/15 Daniel’s program  1981: nucleon-nucleon interaction, looking for a deeper insight justification from Quantum Chromodynamics  Using tools with proven efficiency: Effective force variational methods and mean field theory  An intricate topic with severe issues, gauge invariance, renormalisation …  But interesting results

4 Tribute to Daniel Gogny 08/12/15 Looking for an attractive channel, the effective force, a tricky point Numerical and Mathematical analysis exhibits a competition between 2 phases: - Supraconducting condensate - Bose-Einstein condensate Gluon condensate study within Hartree Fock Bogoliubov mean field theory

5 Tribute to Daniel Gogny 08/12/15 Getting deeper insight relativistic N-body mean field theory In Quantum Electrodynamics A domain where forces are well known … … with operational stakes COMPUTATION OF HEAVY IONS/ATOMS

6 Tribute to Daniel Gogny 08/12/15 From numerical relativistic atomic calculations with Density Functional method Result in accurate eigenstates Plus … A “Spurious” eigenstate Dirac Hamiltonian with Coulomb interaction bounded from below ? Hydrogen-like Iron UU Z > 137 = 1/α

7 Tribute to Daniel Gogny 08/12/15 … back to fundamental issues The BDF QED vacuum is stable if α < 4/π (by « chance », α = 1/137 < 4/ π …) What is the vacuum of QED for relativistic Bogoliubov-Dirac-Fock variational calculations of atoms?

8 Tribute to Daniel Gogny 08/12/15 Meanwhile, the SDIO in USA … Large power Free Electrons Laser Operational capacities for Defence applications ? The ELSA high power, long pulse FEL in CEA

9 Tribute to Daniel Gogny 08/12/15 The non-lineal spectral broadening

10 Tribute to Daniel Gogny 08/12/15

11 Tribute to Daniel Gogny 08/12/15 Exp.Num. Theory Consistent numerical, theoretical and experimental results

12 Tribute to Daniel Gogny 08/12/15 Operational results: FEL can store a significant power … … by loosing laser coherence Except if…

13 Tribute to Daniel Gogny 08/12/15 A part of the heritage: How to identify the most important texts