Relativistic NN scattering equations without partial-wave decomposition

Relativistic quasi-potential equations describing NN scattering are compared. Within the spectator formalism a cancellation is seen to occur between retardation and negative-energy effects.Comment: Talk given at the XVIIth European conference on Few-Body Problems in Physics, \'Evora, Portugal, 11 - 16 September 2000; to be published in Nucl.Phys.

Modelos de educación estética y autoridad interpretativa en centros de arte contemporáneo

Este artículo describe las actividades educativas que ofrecen los centros de arte contemporáneo de nuestro entorno, analizando el rol que se otorga al espectador en las prácticas de interpretación de las obras de arte y el tipo de nociones de arte y comprensión estética que estas prácticas fomentan entre los alumnos. La conclusión propone una nueva noción de comprensión estética y pautas para articular un modelo interpretativo que permita desarrollar actividades educativas de calidad en nuestros centros de arte contemporáneo

Anticorrelation between Ion Acceleration and Nonlinear Coherent Structures from Laser-Underdense Plasma Interaction

In laser-plasma experiments, we observed that ion acceleration from the Coulomb explosion of the plasma channel bored by the laser, is prevented when multiple plasma instabilities such as filamentation and hosing, and nonlinear coherent structures (vortices/post-solitons) appear in the wake of an ultrashort laser pulse. The tailoring of the longitudinal plasma density ramp allows us to control the onset of these insabilities. We deduced that the laser pulse is depleted into these structures in our conditions, when a plasma at about 10% of the critical density exhibits a gradient on the order of 250 {\mu}m (gaussian fit), thus hindering the acceleration. A promising experimental setup with a long pulse is demonstrated enabling the excitation of an isolated coherent structure for polarimetric measurements and, in further perspectives, parametric studies of ion plasma acceleration efficiency.Comment: 4 pages, 5 figure

Three-body correlations in few-body nuclei

A detailed comparison of Faddeev and variational wave functions for ^3H, calculated with realistic nuclear forces, has been made to study the form of three-body correlations in few-body nuclei. Three new three-body correlations for use in variational wave functions have been identified, which substantially reduce the difference with the Faddeev wave function. The difference between the variational upper bound and the Faddeev binding energy is reduced by half, to typically <2\%. These three-body correlations also produce a significant lowering of the variational binding energy for ^4He and larger nuclei

Electronic States in Diffused Quantum Wells

In the present study we calculate the energy values and the spatial distributions of the bound electronic states in some diffused quantum wells. The calculations are performed within the virtual crystal approximation, $sp^3 s^*$ spin dependent empirical tight-binding model and the surface Green function matching method. A good agreement is found between our results and experimental data obtained for AlGaAs/GaAs quantum wells with thermally induced changes in the profile at the interfaces. Our calculations show that for diffusion lengths $L_{D}=20\div100$ {\AA} the transition (C3-HH3) is not sensitive to the diffusion length, but the transitions (C1-HH1), (C1-LH1), (C2-HH2) and (C2-LH2) display large "blue shifts" as L_{D} increases. For diffusion lengths $L_{D}=0\div20$ {\AA} the transitions (C1-HH1) and (C1-LH1) are less sensitive to the L_{D} changes than the (C3-HH3) transition. The observed dependence is explained in terms of the bound states spatial distributions.Comment: ReVTeX file, 7pp., no macros, 4 figures available on the reques