Meson Cloud and SU(3) Symmetry Breaking in Parton Distributions

We apply the Meson Cloud Model to the calculation of nonsinglet parton distributions in the nucleon sea, including the octet and the decuplet cloud baryon contributions. We give special attention to the differences between nonstrange and strange sea quarks, trying to identify possible sources of SU(3) flavor breaking. A analysis in terms of the $\kappa$ parameter is presented, and we find that the existing SU(3) flavor asymmetry in the nucleon sea can be quantitatively explained by the meson cloud. We also consider the $\Sigma^+$ baryon, finding similar conclusions.Comment: 17 pages, LaTeX, 8 figures in .ps file

Hadronic form factors and the J/ψJ/\psi secondary production cross section: an update

Improving previous calculations, we compute the $D + \bar{D} \to J/\psi + \pi$ cross section using the most complete effective lagrangians available. The new crucial ingredients are the form factors on the charm meson vertices, which are determined from QCD sum rules calculations. Some of them became available only very recently and the last one, needed for our present purpose, is calculated in this work.Comment: 12 pages, 9 eps figure

Does the D−/D+D^-/D^+ production asymmetry decrease at large xFx_F?

We have applied the meson cloud model (MCM) to calculate the asymmetries in $D$ and $D_s$ meson production in high energy $\Sigma^-$-nucleus and $\pi^-$-nucleus collisions. We find a good agreement with recent data. Our results suggest that the asymmetries may decrease at large $x_F$.Comment: revised version with new figures and added references to appear in Phys. Rev. Let

Three-dimensional quantum electrodynamics as an effective interaction

We obtain a Quantum Electrodynamics in 2+1 dimensions by applying a Kaluza--Klein type method of dimensional reduction to Quantum Electrodynamics in 3+1 dimensions rendering the model more realistic to application in solid-state systems, invariant under translations in one direction. We show that the model obtained leads to an effective action exhibiting an interesting phase structure and that the generated Chern--Simons term survives only in the broken phase.Comment: 10 pages in Plain Te

Macroeconomic effects of fiscal consolidations in a DSGE model for the Euro Area: does composition matter?

We develop a new-Keynesian DSGE model with an extended fiscal policy block to assess the conditions for expansionary fiscal consolidations. In addition to several taxes, we consider public employment expenditures and government spending, which may have different degrees of productivity. We calibrate the model for the Euro Area and use it to simulate alternative fiscal consolidations with changes in the budget composition. Among the main conclusions we find that: (i) if conducted with a cut in weaklyproductive spending and a symmetric increase in highly-productive spending, fiscal consolidations have expansionary effects on investment and output; (ii) if consolidation is pursued through a pure reduction in weaklyproductive public employment, the effects on output decrease with the degree of labor market competition and turn out to be positive under perfect competition.fiscal policy, fiscal consolidation, new-Keynesian DSGE model