Medames et Mesieurs,

Je voudrais commencer par remercier

· M. Frédéric Fleury, Président de l'Universite de Lyon,

· M. Hamda Ben Hadid, Président du conseil académique, et

· M. Fabrice Vallée, Président du conseil scientifique,

pour m'avoir accordé l'honneur d'obtenir le titre de Docteur Honoris Causa de l'Université.

Je voudrais également remercier M. Guy Chanfray, Directeur de l'IPNL, et M. Jean-Claude Plenet, Directeur du Département de Physique pour leur soutien continu au groupe de physique nucléaire théorique, le soutien qui nous a permis de poursuivre nos directions de recherche.

Mais je voudrais tout particulièrement remercier mon collègue, collaborateur et ami Karim Bennaceur, ainsi que d'autres membres du groupe de physique nucléaire, d'avoir eu l'idée de me désigner pour cet honneur spectaculaire que je reçois aujourd'hui.

En effet, je considère la reconnaissance par les confrères comme étant au sommet des valeurs que l'on peut obtenir dans la vie scientifique. Et même si la plupart des propositions similaires aboutisent á rien, ce qui n'est pas si rare, si je peux vous le dire, la reconnaissance comme ça restera toujours dans mon cœur et deviendra la récompense la plus importante pour le dur travail d'un scientifique.

Après les 43 années de mon service académique, je n’aucun doute que mes liens avec la France étaient particulièrement significatifs. En ajoutant tous mes séjours dans votre pays, j'arrive à un chiffre de cinque années de ma vie. Mon premier poste après mon doctorat était à l'Institut de Physique Nucléaire d'Orsay - je l'ai commencé en 1981. Après beaucoup d'autres séjours à Orsay, Saclay et Strasbourg, ma collaboration principale est maintenant avec le groupe à Lyon.

C'est qui est tout à fait naturel, si on constate que dans mon domaine de recherche, la France est, et a toujours été, au centre du progrès et du développement de nouvelles idées.

Comme je voudrais maintenant vous parler un peu de la science que je fais, permettez-moi de cesser de vous tourmenter avec mon français déjà un peu rouillé et de continuer en anglais.

Nuclear physics is a mature domain of science. Atomic nucleus has been discovered over a hundred years ago in a famous experiment performed by Rutherford, who was irradiating a thin foil of gold with alpha radiation. In a complete surprise, he realized that some particles where reflected back from the foil, instead of smoothly going through. It was as strange as if you had shot a bullet towards a sheet of paper, and it was reflected back on you. The best explanation of the phenomenon was that matter is composed of very small compact objects in centres of atoms - of the nuclei.

Today we know that the atomic nucleus is a composite object built of protons and neutrons. Let me give you one specific example of the atomic nucleus, the oganesson-294. Most of you probably never heard abut the chemical element called oganesson. Well, I am not surprised, because it has been discovered only a few years ago, and its name, deriving from the family name a Russian scientist, Youri Oganessian, was coined only last year. Oganesson-294 is the heaviest chemical element known to humanity. Its nucleus contains 118 protons and 176 neutrons.

Over a many-months irradiation by a beam of heavy calcium nuclei impinging on a target of very heavy material built of californium, only a few species of oganesson-294 were produced, and every one of those decayed after a few milliseconds of time.

A truly ephemeral object of nature, isn’t it?

One can justly wonder why on earth physicists do care about such objects, and why do they spend hundreds of millions of euros of good taxpayer money to hunt for those. The truth is that the humanity pursues these ghosts simply out of curiosity. How the matter is built? How was it created? What are the limits of its existence? These are the questions we try to answer in nuclear physics.

To those who are still not convinced, I would like to quote Michael Faraday, who discovered a method to produce electric current. He once was asked what on earth would be the use of such ephemeral thing, which nobody was able even to see. He said "I really do not know, but one day, Her Majesty may tax it".

You must have certainly started wondering by know what exactly I am doing in my research. Let me come back to our oganesson-294, which is built out of 294 constituent particles. Imagine now a village of 294 inhabitants, 118 men and 176 women to make the analogy complete. The social structure of this community is a result of numerous social interactions between pairs: husband-wife, father-son, mother-son, mother-daughter, neighbour-neighbour, priest-sinner, seller-buyer, chimney sweeper-house owner, etc. But can we predict how the community will develop based on these binary interactions? It seems like a daunting, impossible task, because there are simply to many combinations to consider.

Well, it is equally impossible to describe properties of oganesson-294 by considering all possible interactions between protons and neutrons. My research thus aims at simplifying the problem. We try to devise theories that would describe this composite system as a whole. Can there be general rules that govern its structure? Are there emerging phenomena, which appear when the whole becomes more than a mere sum of its constituents? In nuclear physics, such questions can be answered within an approach called density functional theory. In a nut shell, we attempt to describe the structure of the village by considering its overall characteristics, like the density of population or flows of the population when inhabitants go about their daily businesses, instead of detailed information about the social interactions between pairs of individuals.

Of course, the reality is somewhat less glamorous; in our everyday life, we simply program large computers and write scientific publications. Nevertheless, as you certainly know: to do science is an enormous joy and pleasure, and as a cherry ontop, they even sometimes confer on you a Doctorate Honoris Causa.