Over 50 participants from around the world gathered at the nearby Institut Pascal last month to ponder the mysteries of quantum gravity and conformal field theory, in a workshop entitled "Speakable and Unspeakable in Quantum Gravity," co-organized by IPhT researchers Dalimil Mazáč and Eric Perlmutter (alongside colleagues Lorenz Eberhardt and Ida Zadeh).

The three-week program, from May 13-31, aimed to crystallize the state-of-the-art at the interface of these two subjects, starting from the seemingly innocuous idea that any universe with gravity should obey certain well-established physical principles, such as the positivity of energy and the requirement that probabilities always add up to one; these principles may then be leveraged to rigorously constrain the properties of quantum gravity

Recent years have seen rapid progress in this "bootstrap" approach to the consistency of fundamental theory. The main goal of the workshop was to consolidate existing threads, and sharpen quantitative approaches to the question of how, indeed, gravity must behave at the quantum level. Designed to emphasize forward-looking discussions and interaction, the program featured a very relaxed schedule of seminars alongside weekly moderated discussions — on dynamics of black holes, string theory scattering amplitudes, ensembles of quantum systems, random matrices, and the search for "simple" theories of gravity. The international audience consisted of postdoctoral and more senior researchers, for whom the Institut Pascal was an ideal gathering venue.

One eagerly anticipates the culmination of original ideas and breakthroughs that have emerged from this workshop!