Can the meson cloud explain the nucleon strangeness?

We use the meson cloud model, including the kaon and the $K^*$ contributions, to estimate the electric and magnetic strange form factors of the nucleon. We compare our results with the recent measurements of the strange quark contribution to parity-violating asymmetries in the forward G0 electron-proton scattering experiment. We conclude that it is not possible to explain the data using this model.Comment: version accepted for publication in Phys. Rev.

Advanced solid elements for sheet metal forming simulation

The solid-shells are an attractive kind of element for the simulation of forming processes, due to the fact that any kind of generic 3D constitutive law can be employed without any additional hypothesis. The present work consists in the improvement of a triangular prism solid-shell originally developed by Flores [2, 3]. The solid-shell can be used in the analysis of thin/thick shell, undergoing large deformations. The element is formulated in total Lagrangian formulation, and employs the neighbour (adjacent) elements to perform a local patch to enrich the displacement field. In the original formulation a modified right Cauchy-Green deformation tensor (C¯) is obtained; in the present work a modified deformation gradient (F¯) is obtained, which allows to generalise the methodology and allows to employ the Pull-Back and Push-Forwards operations. The element is based in three modifications: (a) a classical assumed strain approach for transverse shear strains (b) an assumed strain approach for the in-plane components using information from neighbour elements and (c) an averaging of the volumetric strain over the element. The objective is to use this type of elements for the simulation of shells avoiding transverse shear locking, improving the membrane behaviour of the in-plane triangle and to handle quasi-incompressible materials or materials with isochoric plastic flow.Postprint (published version

Investigating different structures for the X(3872)X(3872)

Using the QCD spectral sum rule approach we investigate different currents with $J^{PC}=1^{++}$, which could be associated with the $X(3872)$ meson. Our results indicate that, with a four-quark or molecular structure, it is very difficult to explain the narrow width of the state unless the quarks have a special color configuration.Comment: 4 pages. Contribution to the proceedings of the 15th International QCD Conference (QCD10

A rotation free shell triangle with embedded stiffeners

In this paper a rotation free shell element with embedded stiffeners is presented. The element is based on a previous one where the membrane and bending strains are obtained using a patch of four triangular elements centered on the analyzed one. The stiffener is located between two adjacent elements, thus its position is defined by the two end nodes of the corresponding triangle side. The curvature of the stiffener in the tangent plane to the surface is disregarded as it is assumed that the surface is quite rigid in its plane. The torsion and surface normal curvature of the stiffener are computed from the curvatures of its two adjacent elements. A classical beam theory is used for the stiffener disregarding shear strains while the axial strain is standard. An example is presented for a preliminary assessment of the developed element

Tightly coupled computational fluid and crowd dynamics via immersed boundary methods

A methodology to couple computational fluid and computational crowd dynamics (CFD, CCD) has been developed. Technological advances that made this possible include: a) Mature CFD and CCD codes/solvers; b) Development of immersed boundary methods for moving bodies (CFD); c) Strong scaling to tens of thousands of cores (CFD); and d) Implementation of fast search techniques for information transfer between codes (CFD, CCD). We consider that tightly coupled simulations such as the ones presented here will lead to more realistic evacuation studies where fire, smoke, visibility and inhalation of toxic materials influence the motion of people, and where a large crowd can block or influence the flow in turn. Cases where this may occur are metro-stations, high-rise buildings and indoor sports arenas, where a crowd can block a considerable portion of the passage area, thereby influencing the flow

QCD sum rule approach for the light scalar mesons as four-quark states

We study the two point-function for the scalar mesons $\sigma, \kappa, f_0(980)$ and $a_0(980)$ as diquak-antidiquark states. We also study the decays of these mesons into $\pi\pi$, $K\pi$ and $K\bar{K}$. We found that the couplings are consistent with existing experimental data, pointing in favor of the four-quark structure for the light scalar mesons.Comment: 6 pages, 4 figure