## Interview with Cédric Villani

On 21 May this year, CERN had the pleasure of welcoming the mathematician Cédric Villani as part of the series of lectures organised by the *Groupement des Français du CERN*. The *CERN Bulletin* took the opportunity to ask him a few questions.

*CERN Bulletin:***This is your first visit to CERN –** **how have you found it?**

**Cédric Villani:** It has been instructive and moving, both because of the theoretical research that CERN makes possible and because of the technological feat that it represents – truly a technological work of art!

*CERN Bulletin:***You are currently working on Riemannian geometry problems.** **Is there any link between this work and the research carried out at CERN?**

**Cédric Villani:** All the work that I’ve done in mathematical physics builds on classical physics problems – problems that do not require me to draw on quantum mechanics, relativistic mechanics, infinitesimal or infinite quantities. In this sense, my work is completely unrelated to CERN’s research. That said, a page in the history of physics is being written here now, and one can’t help being interested.

*CERN Bulletin:***CERN enjoys an undeniably cosmopolitan working environment.** **Do you think that this is an asset for scientific research?**

**Cédric Villani:** European cooperation comes into its own when there is a large project to be realised for which it's really essential to pool our expertise, whether for CERN, ITER or ESA and so on. CERN is a very good example of what the countries of Europe can do when they join forces.

*CERN Bulletin:***The discovery of the Higgs boson is the successful culmination of many years of research.** **What are your thoughts on the subject?**

**Cédric Villani:** The discovery of the Higgs boson is an extraordinary accomplishment! The verification of this theory has required the deployment of considerable resources; it is pretty impressive, all of this technology built to serve the human mind. Putting it rather more grandiosely, we could say that it is a real triumph of the human mind over what we don’t understand. After the event, critics will say that it was a bit of a let-down in the end, as it is exactly what was expected. What are we going to do now?! I have confidence in my high energy colleagues to answer that question; they will find worthwhile projects to take on and fascinating theories to test.

*CERN Bulletin:***If you could uncover the answer to one of the mysteries of mathematical physics, which one would you choose?**

**Cédric Villani:** Phase transition, without a doubt. What is its ultimate mathematical genesis? That’s an essential question. It’s not a yes or no question - we know that phase transitions occur - it's more a question of how. For mathematicians, the more important question is often “Why is such-and-such a phenomenon true?” rather than “Is this phenomenon true?”

*CERN Bulletin:***What would you be doing if you hadn't pursued mathematics?**

**Cédric Villani:** As a child, my passion was palaeontology. It’s a very difficult discipline, involving a lot of painstaking work. Imagination, tenacity and rigour are the three qualities of both the palaeontologist and the mathematician. In mathematics, imagination is perhaps the most important; in palaeontology, it is undoubtedly tenacity.

*Interview by Anaïs Schaeffer*