A variational approach to approximate particle number projection with effective forces

Kamlah's second order method for approximate particle number projection is applied for the first time to variational calculations with effective forces. High spin states of normal and superdeformed nuclei have been calculated with the finite range density dependent Gogny force for several nuclei. Advantages and drawbacks of the Kamlah second order method as compared to the Lipkin-Nogami recipe are thoroughly discussed. We find that the Lipkin-Nogami prescription occasionally may fail to find the right energy minimum in the strong pairing regime and that Kamlah's second order approach, though providing better results than the LN one, may break down in some limiting situations.Comment: 16 pages, 8 figure

Hume, Popper: el conocimiento de las determinaciones de objeto.

Sin resume

El empirismo y su método.

Sin resume

GCM Analysis of the collective properties of lead isotopes with exact projection on particle numbers

We present a microscopic analysis of the collective behaviour of the lead isotopes in the vicinity of Pb208. In this study, we rely on a coherent approach based on the Generator Coordinate Method including exact projection on N and Z numbers within a collective space generated by means of the constrained Hartree-Fock BCS method. With the same Hamiltonian used in HF+BCS calculations, we have performed a comprehensive study including monopole, quadrupole and octupole excitations as well as pairing vibrations. We find that, for the considered nuclei, the collective modes which modify the most the conclusions drawn from the mean-field theory are the octupole and pairing vibrations.Comment: 10 pages LATEX, 8 figures, submitted to EPJ

Kinetics of recovery from anhydrobiosis in Pratylenchus thornei, Merlinius brevidens and Heterodera avenae from dry field soils and dry roots of the host plant

Le comportement de #Pratylenchus thornei, Merlinius brevidens et #Heterodera avenae dans un sol particulièrement sec du sud de l'Espagne a été étudié, après la saison d'été. Six périodes de récupération, allant jusqu'à 135 h de réhydratation suivie de migration, permettent de récupérer plus de 95 % de la population de #Merlinius$. Mais, pour "P. thornei$ - qui semble l'espèce dominante et la plus importante dans la zone considérée - la récupération au taux de 95 %, après culture de blé var, yecora, n'est atteinte qu'après douze périodes, et 279 h, pour autant que toutes les racines présentes dans le sol soient elles aussi traitées. Les #Pratylenchus survivant dans les racines desséchées du blé semblent être la cause de pertes de récolte encore inexpliquées atteignant cette culture. #Heterodera avenae ne paraît jouer qu'un rôle secondaire dans ces sols secs. (Résumé d'auteur

On the field anhydrobiotic ability of Pratylenchis thornei and Merlinius brevidens

La présente étude du comportement anhydrobiotique de #Pratylenchus thornei et de #Merlinius brevidens a été réalisée dans un champ non irrigué de blé cv. Gallareta, variété considérée comme non-hôte ou mauvais hôte pour ces nématodes. #P. thornei paraît plus dépendant de l'humidité du sol que #M. brevidens en ce qui concerne sa récupération après 15 h de migration (réhydratation, réactivation et migration). #M. brevidens sort plus facilement de son état anhydrobiotique. Les schémas d'émergence sont semblables pour les deux nématodes qu'ils soient actifs ou récupérés après une anhydrobiose prononcée. Ces schémas sont par contre différents s'il s'agit d'un stade précoce d'anhydrobiose (anhydrobiose modérée). Les deux nématodes font montre, en relation avec la profondeur du sol, d'une inertie à entrer en anhydrobiose qui paraît dépendre des processus naturels de dessiccation du sol du champ. Cette inertie semble plus prononcée chez #M. brevidens. (Résumé d'auteur

Approximate particle number projection with density dependent forces: Superdeformed bands in the A=150 and A=190 regions

We derive the equations for approximate particle number projection based on mean field wave functions with finite range density dependent forces. As an application ground bands of even-A superdeformed nuclei in the A=150 and A=190 regions are calculated with the Gogny force. We discuss nuclear properties such as quadrupole moments, moments of inertia and quasiparticle spectra, among others, as a function of the angular momentum. We obtain a good overall description.Comment: 31 pages, 10 figures, 3 appendices. In press in Nucl. Phy

Configuration mixing of mean-field wave-functions projected on angular momentum and particle number; application to 24Mg

We present in this paper the general framework of a method which permits to restore the rotational and particle number symmetries of wave functions obtained in Skyrme HF+BCS calculations. This restoration is nothing but a projection of mean-field intrinsic wave functions onto good particle number and good angular momentum. The method allows also to mix projected wave functions. Such a configuration mixing is discussed for sets of HF+BCS intrinsic states generated in constrained calculations with suitable collective variables. This procedure gives collective states which are eigenstates of the particle number and the angular momentum operators and between which transition probabilities are calculated. An application to 24Mg is presented, with mean-field wave functions generated by axial quadrupole constraints. Theoretical spectra and transition probabilities are compared to the experiment.Comment: 26 pages, 7 figures. Submitted to Nuclear Physic