Organizing commitee: Brando Bellazzini, John Joseph Carrasco and Filippo Vernizzi

Single (top) vs double copy (bottom) theory This past year a team at IPhT around John Joseph Carrasco — in collaboration with physicists at UCLA and Penn State University in the United States, and Uppsala University in Sweden — completed a calculation long thought to be impossible: the direct understanding of the dimensions of space-time in which the most symmetric particle-based field theory of gravity (maximal supergravity) would cease to be predictive when quantum effects are relevant. One can isolate order by order the quantum effects in graviton scattering. For two gravitons scattering off of each other, this calculation required consideration of the fifth-order quantum correction. This puts strong constraints on the behavior of fundamental symmetries in controlling the high-energy behavior of this theory.

Periodically driven quantum many-body systems (such as cold atoms in time-dependent optical lattices and quantum materials under ultra-fast optical excitation) offer exciting perspectives of exploring quantum phases of matter along genuine non-equilibrium pathways.This so-called Floquet engineering relies, however, on the suppression of heating, i.e. the uncontrolled energy absorption from the drive. This was known to be the case only in the limit of extremely high frequency,thus limiting its practical use. A team at IPhT around Francesco Peronaci, Marco Schiro and Olivier Parcollet showed that also strong electronic interactions can largely circumvent energy absorption, and thus provide a robust platform for Floquet engineering even at finite frequency. This is demonstrated with non-equilibrium dynamical mean-field calculations on a driven Fermi-Hubbard model, a paradigmatic example of lattice correlated electrons.

We are happy to learn that Michel Gaudin has been awarded the 2019 Dannie Heineman Prize for Mathematical Physics, together with Bill Sutherland (U. of Utah) and F. Calogero (U. di Roma La Sapienza), for their "... profound contributions to the field of exactly solvable models in statistical mechanics and many body physics, in particular the construction of the widely studied Gaudin magnet and the Calogero-Sutherland, Shastry-Sutherland, and Calogero-Moser models." This prize was established in 1959 by the Heineman Foundation for Research, Educational, Charitable, and Scientific Purposes, Inc., and is administered jointly by the American Physical Society and the American Institute of Physics. It recognizes outstanding publications in the field of mathematical physics. Michel Gaudin entered CEA in 1956 and is one of the "grands anciens" of what is now IPhT.

Bertrand Eynard (IPhT) has been awarded an ERC Synergy grant, "Recursive and Exact New Quantum Theory", together with J.E. Andersen (QGM, Aarhus University, DK), B. Eynard (IPhT), Mr. Kontsevich (IHES, Bures-sur-Yvette) and M. Mariño (UNIGE, Geneva, CH). Two other IPhT researchers are involved in this project. The Synergy Grants aim to establish collaborations between several researchers in different institutes on a common program. The goal of the ReNewQuantun program is to build new foundations for quantum field theory, beyond perturbation theory, by using advanced geometric and topological methods (topological recursion, geometric recursion, resurgence theory, non-linear Riemann-Hilbert methods, Fukaya categories, topological string theories, mirror symmetry, etc.). This program should open new avenues for exploring the relations between gravitation and quantum mechanics, and for incorporating it into unified theories of fundamental interactions.

Stéphane Lavignac (IPhT) vient de publier avec Antoine Kouchner, directeur du laboratoire Astroparticule et Cosmologie de l’Université Paris-Diderot, un livre de vulgarisation sur les neutrinos : « A la recherche des neutrinos – messagers de l’infiniment grand et de l’infiniment petit », collection « Quai des Sciences », éditions Dunod. Dépourvus de charge électrique, dotés de masses très petites et interagissant très faiblement avec la matière, les neutrinos comptent parmi les particules élémentaires les plus mystérieuses. Introduits presque en catimini par Wolfgang Pauli en 1930, dans une tentative désespérée de sauver le principe de conservation de l’énergie, les neutrinos n’ont eu de cesse d’intriguer les physiciens.