Leo Gershoy, vecteur ukraino-américain de l'historiographie de la Révolution

L’intérêt de faire entrer Leo Gershoy dans les échanges franco-américains de l’historiographie de la Révolution française est de prendre, dès les années 1925, un prisme doublement décalé des autorités et conventions parisiennes à partir de son travail sur Bertrand Barère, dont il fut et reste le biographe majeur. Il qualifie le personnage d’« unheroic » puis, en 1962, dans un dernier ouvrage, de « reluctant terrorist », au fil d’une lecture non strictement idéologique du fait partisan et de la pratique du pouvoir en révolution. Sa sensibilité à un marxisme dissident, celui des anarcho-russes des États-Unis, renforcé de son origine de juif ukrainien parti enfant de Kryvyi-Rih (Krivoï-Rog) le mènent à considérer l’exercice de l’exécutif et sa légitimité face à la questions cruciale de ce qui fait nation en situation de guerre pour 1917-1921, puis sous le surplomb dirimant des camps en présence après la Seconde Guerre mondiale, suivie de la Guerre froide. Le souci souterrain de comprendre les hésitations et compromis, le statut de l’adversaire, minorité politique, mais on pourrait ajouter religieuse ou ethnique, fondent une curiosité et des choix de chantiers dont le personnage de Bertrand Barère est le révélateur

Aux bonheurs du XIXe siècle

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Double Λ\Lambda and the Λ−Λ\Lambda-\Lambda Interaction

The $\Lambda$-$\Lambda$ effective interaction, in the channel $L=S=0$, in the nuclear medium is fitted to the available binding energies, $B_{\Lambda\Lambda}$, of double $\Lambda$ hypernuclei: $^{6}_{\Lambda\Lambda}$He, $^{10}_{\Lambda\Lambda}$Be and $^{13}_{\Lambda\Lambda}$B. The mesonic decay of these hypernuclei is also investigated. Finally, this effective interaction is used to predict the binding energies and mesonic decays widths of heavier double $\Lambda$ hypernuclei.Comment: 4 pages, (latex file, postscript-file and 3 Postscript-figures included

Bertrand Barère, lecteur de Pascal

Le commentaire que nous présentons ici fut écrit en 1818 par Barère, l’ancien rapporteur du Comité de Salut public ; celui qui fut la « voie de la Révolution », l’« Anacréon de la guillotine » selon une expression du temps, n’était plus alors qu’un « homme sans nom » à la manière du héros de Ballanche. Régicide rallié aux Cent-jours, il ne pouvait aucunement bénéficier de la loi dite d’amnistie du 12 janvier 1816. Réfugié à Mons et seul à vivre sous nom d’emprunt parmi les exilés qui trouvère..

Quark-meson coupling model with constituent quarks: Exchange and pionic effects

The binding energy of nuclear matter including exchange and pionic effects is calculated in a quark-meson coupling model with massive constituent quarks. As in the case with elementary nucleons in QHD, exchange effects are repulsive. However, the coupling of the mesons directly to the quarks in the nucleons introduces a new effect on the exchange energies that provides an extra repulsive contribution to the binding energy. Pionic effects are not small. Implications of such effects on observables are discussed.Comment: 12 pages, latex, 1 figure, to appear in Phys. Lett.

Neutron rich nuclei in density dependent relativistic Hartree-Fock theory with isovector mesons

Density dependent relativistic Hartree-Fock theory has been extended to describe properties of exotic nuclei. The effects of Fock exchange terms and of pi - and rho - meson contributions are discussed. These effects are found to be more important for neutron rich nuclei than for nuclei near the valley of stability.Comment: 10 pages, 5 figures, LaTeX, macro packages graphicx and time

Spin-Orbit Splitting in Non-Relativistic and Relativistic Self-Consistent Models

The splitting of single-particle energies between spin-orbit partners in nuclei is examined in the framework of different self-consistent approachs, non-relativistic as well as relativistic. Analytical expressions of spin-orbit potentials are given for various cases. Proton spin-orbit splittings are calculated along some isotopic chains (O, Ca, Sn) and they are compared with existing data. It is found that the isotopic dependence of the relativistic mean field predictions is similar to that of some Skyrme forces while the relativistic Hartree-Fock approach leads to a very different dependence due to the strong non-locality.Comment: 12 pages, RevTeX, 4 new figs.in .zip format, unchanged conclusions, Phys. ReV.

On the relativistic origin of the kink effect in the chain of Pb isotopes

We investigate the origin of the kink effect (KE) in the relativistic mean field theory by transforming the single-particle Dirac equation into a Schrodinger-like equation. It is found that relativistic self-consistent effects as well as contributions from the rho meson determine the actual structure of the KE. However, the spin-orbit force generated by the rho meson has no significant influence on the KE.Comment: 11 pages, RevTeX, 3 postscript figs., Phys. Lett.

Neutron Stars and Nuclei in the Modified Relativistic Hartree Approximation

We have examined the properties of neutron-rich matter and finite nuclei in the modified relativistic Hartree approximation for several values of the renormalization scale, $\mu$, around the standard choice of $\mu$ equal to the nucleon mass $M$. Observed neutron star masses do not effectively constrain the value of $\mu$. However for finite nuclei the value $\mu/M=0.79$, suggested by nuclear matter data, provides a good account of the bulk properties with a sigma mass of about 600 MeV. This value of $\mu/M$ renders the effective three and four body scalar self-couplings to be zero at 60\% of equilibrium nuclear matter density, rather than in the vacuum. We have also found that the matter part of the exchange diagram has little impact on the bulk properties of neutron stars.Comment: 33 pages, Latex, 8 figures (available from authors by fax), Minnesota preprint NUC-MINN-93/7-

Fock terms in the quark-meson coupling model

The mean field description of nuclear matter in the quark-meson coupling model is improved by the inclusion of exchange contributions (Fock terms). The inclusion of Fock terms allows us to explore the momentum dependence of meson-nucleon vertices and the role of pionic degrees of freedom in matter. It is found that the Fock terms maintain the previous predictions of the model for the in-medium properties of the nucleon and for the nuclear incompressibility. The Fock terms significantly increase the absolute values of the single-particle, four-component scalar and vector potentials, a feature that is relevant for the spin-orbit splitting in finite nuclei.Comment: RevTex, 17 pages, 4 Postscript figures, version to appear in Nucl. Phys.