Evolution of the N=28 shell closure: a test bench for nuclear forces

The evolution of the N=28 shell closure is investigated far from stability. Using the latest results obtained from various experimental techniques, we discuss the main properties of the N=28 isotones, as well as those of the N=27 and N=29 isotones. Experimental results are confronted to various theoretical predictions. These studies pinpoint the effects of several terms of the nucleon-nucleon interaction, such as the central, the spin-orbit, the tensor and the three-body force components, to account for the modification of the N=28 shell gap and spin-orbit splittings. Analogies between the evolution of the N=28 shell closure and other magic numbers originating from the spin-orbit interaction are proposed (N=14,50, 82 and 90). More generally, questions related to the evolution of nuclear forces towards the drip-line, in bubble nuclei, and for nuclei involved in the r-process nucleosynthesis are proposed and discussed.Comment: 40 pages,15 figures, Procceedings Nobel Symposium 2012, accepted for publication in Physica Script

Springer basic sets and modular Springer correspondence for classical types

We define the notion of basic set data for finite groups (building on the notion of basic set, but including an order on the irreducible characters as part of the structure), and we prove that the Springer correspondence provides basic set data for Weyl groups. Then we use this to determine explicitly the modular Springer correspondence for classical types (for representations in odd characteristic). In order to do so, we compare the order on bipartitions introduced by Dipper and James with the order induced by the Springer correspondence.Comment: 31 page

The Alteration de Kingsley Amis : un essai de linguistique surveillée

In The Alteration, Kingsley Amis tries to imagine what might have happened if the Protestant Reformation had never occurred. But Amis's alternate world is first and foremost a linguistic uchronia: a constant effort is required from the reader to persuade him/herself that the story is taking place in 1976 as language seems to belong to bygone days. Language has fallen prey to the Catholic repression exercised on minds and bodies: the Anglo-Saxon heritage has been exterminated to the profit of a romanised English version that seems to have stopped evolving. Indeed, just as alteration is practised on human beings --in particular, the young prodigious singer Hubert Anvil-- and more generally, just as all forms of desire have been repressed, language in The Alteration is an altered language stretching out into cumbersome sentences laden with parentheses and hyphens, forbidding any linguistic fluidity. The flux of desire is stifled by this standardized and standardizing language, some linguistic Thanatos keeping people on probation.Dans The Alteration, Kingsley Amis essaie d'imaginer ce qui se serait passé si la Réforme n'avait pas eu lieu. Mais l'histoire alternative de Amis est avant tout une uchronie linguistique: il faut au lecteur un effort constant pour se persuader que l'histoire se déroule en 1976 tant le langage qui lui est donné à lire semble appartenir à une époque révolue. La répression exercée par le pouvoir catholique sur les corps et les esprits s'est depuis longtemps opérée sur le langage : l'héritage anglo-saxon a été exterminé au profit d'une version anglaise romanisée qui semble figée dans le temps. En effet, à l'image de la castration ("alteration") pratiquée sur les êtres (en particulier le jeune chanteur prodige Hubert Anvil) et du refoulement généralisé du désir et de la production, le langage de The Alteration est un langage castré s'étirant dans de lourdes phrases encombrées de parenthèses et de tirets qui interdisent toute fluidité linguistique. C'est en effet le flux du désir qu'étouffe ce langage uniforme et uniformisant, véritable thanatos langagier qui maintient les hommes en liberté surveillée

Evolution of the N=50 gap from Z=30 to Z=38 and extrapolation towards 78Ni

The evolution of the N=50 gap is analyzed as a function of the occupation of the proton f5/2 and p3/2 orbits. It is based on experimental atomic masses, using three different methods of one or two-neutron separation energies of ground or isomeric states. We show that the effect of correlations, which is maximized at Z=32 could be misleading with respect to the determination of the size of the shell gap, especially when using the method with two-neutron separation energies. From the methods that are the least perturbed by correlations, we estimate the N=50 spherical shell gap in 78Ni. Whether 78Ni would be a rigid spherical or deformed nucleus is discussed in comparison with other nuclei in which similar nucleon-nucleon forces are at play.Comment: 7 pages, 8 figures, accepted for publication PRC (22 december 2011

Shell Evolutions and Nuclear Forces

7 pages, 5 figures, Talk given at the 25th International Nuclear Physics Conference (INPC), Firenze, Italy, 2-7 June 2013International audienceDuring the last 30 years, and more specifically during the last 10 years, many experiments have been carried out worldwide using different techniques to study the shell evolution of nuclei far from stability. What seemed not conceivable some decades ago became rather common: all known magic numbers that are present in the valley of stability disappear far from stability and are replaced by new ones at the drip line. By gathering selected experimental results, beautifully consistent pictures emerge, that very likely take root in the properties of the nuclear forces.The present manuscript describes some of these discoveries and proposes an intuitive understanding of these shell evolutions derived from observations. Extrapolations to yet unstudied regions, as where the explosive r-process nucleosynthesis occurs, are proposed. Some remaining challenges and puzzling questions are also addressed

Gamma Spectroscopy of Nuclei far for Stability

The focus of the present review is the study of neutron-rich medium-mass nuclei around major shells or subshells N=20, 28 or 40. Coulomb excitation of secondary beams and in-beam spectroscopy study using the fragmentation of a stable beam have brought a wealth of informations concerning the behaviour of the closed shells when nuclei contain large neutron excesses. Pionneering experiments in this field are presented with special emphasis on the work achieved at the Ganil accelerator