The baryon-decuplet in the chiral dynamics of Lambda-hyperons in nuclear matter

We study the long range part of the $\Lambda$-hyperon optical potential in nuclei using Quantum Many Body techniques and flavor-SU(3) Chiral Lagrangians as starting point. More precisely, we study the contributions to the $\Lambda$-hyperon optical potential due to the long-range two-pion exchange, with $\Sigma$ and $\Sigma^*$ baryons in the internal baryonic lines and considering Nh and $\Delta$h excitations. We also consider the contribution to the spin-orbit potentials that comes out from these terms. Our results support a natural explanation of the smallness of the $\Lambda$-nuclear spin-orbit interaction and shows the importance of the $\Sigma^*$ and $\Delta$ degrees of freedom for the hyperon-nucleus interactions.Comment: 8 pages, 5 figure

Vertical motions in the disk of NGC 5668 as seen with optical Fabry-Perot spectroscopy

We have observed the nearly face-on spiral galaxy NGC 5668 with the TAURUS II Fabry-Perot interferometer at the William Herschel Telescope using the $H\alpha$ line to study the kinematics of the ionized gas. From the extracted data cube we construct intensity, velocity and velocity dispersion maps. We calculate the rotation curve in the innermost 2 arcmin and we use the residual velocity field to look for regions with important vertical motions. By comparing the geometry of these regions in the residual velocity field with the geometry in the intensity and velocity dispersion maps we are able to select some regions which are very likely to be shells or chimneys in the disk. The geometry and size of these regions are very similar to the shells or chimneys detected in other galaxies by different means. Moreover, it is worth noting than this galaxy has been reported to have a population of neutral hydrogen high velocity clouds (Schulman et al. 1996) which, according to these observations, could have been originated by chimneys similar to those reported in this paper.Comment: 7 pages with 9 figures. LaTeX file using A&A v4.0 macro

Existence and uniqueness of nontrivial collocation solutions of implicitly linear homogeneous Volterra integral equations

We analyze collocation methods for nonlinear homogeneous Volterra-Hammerstein integral equations with non-Lipschitz nonlinearity. We present different kinds of existence and uniqueness of nontrivial collocation solutions and we give conditions for such existence and uniqueness in some cases. Finally we illustrate these methods with an example of a collocation problem, and we give some examples of collocation problems that do not fit in the cases studied previously.Comment: 18 pages, 4 figure

Nucleon Emision Off Nuclei Induced By Neutrino Interactions

We make a review of the main nuclear effects that affect neutrino-nucleus cross sections. We discuss how the different models in the literature try to describe these different effects, and thus try to compare between them. We focus on the quasi-elastic reaction in the neutrino energy region of around 1 GeV, where recent data from MiniBoone are available. Among the issues discussed are the different treatment of medium corrections to initial and nal state nucleon wave functions and the problem of the rescattering of ejected nucleons.Comment: 5 pages, 5 figures. To appear in the proceedings for NuFact09; July 20-25, (2009) Illinois Institute of Technolog