We carry out a systematic investigation of twist-two spin dependent structure functions of the nucleon within the framework of the chiral quark soliton model (CQSM) by paying special attention to the role of chiral symmetry of QCD. The importance of chiral symmetry is illustrated through the good reproduction of the recent SLAC data for the neutron spin structure function gn 1 (x,Q 2). We also ...

We calculate the imaginary part of the induced pseudoscalar form factor of the nucleon GP (t) in the framework of two-loop heavy baryon chiral perturbation theory. The effect of the calculated three-pion continuum on the pseudoscalar constant gP = (mμ/2M)GP (t = −0.877mμ) measurable in ordinary muon capture μp → νμn turns out to be negligibly small. Possible contributions from counterterms at t...

In this paper, the passive control of flow past a semi-circular cylinder is investigated. This control is achieved by adding a porous medium between the solid obstacle and the incompressible fluid in order to reduce drag forces and regularize the flow. A vortex-penalization method is chosen to easily model the flow in the different media. Several configurations of the porous layer are investiga...

Helicity distributions of valence quarks have been investigated in many experiments and are now well known. On the other hand, the distributions of the polarized sea are poorly known. In particular, concerning ∆ū(x), fits assuming a totally flavour symmetric sea suggest a sign opposite respect to fits based on a flavour broken sea . The situation is even more confused concerning the transversit...

I outline some of the most recent developments in the global fit to parton distributions performed by the MRST collaboration. At present there is a great deal of interest in the importance of parton distributions for studies at the LHC. This necessarily involves a certain kinematic range for the partons. The kinematic range for particle production at the LHC is shown in fig. 1. Parton distribut...

with a specially selected initial data v̄0(x). The optimal convergence rates ‖∂ x (v− v̄, u− ū)(t)‖L2 = O(1)(t 2k+3 4 , t 2k+5 4 ), k = 0, 1, are also obtained, as the initial perturbation is in L(R+) ∩ H(R+). If the initial perturbation is in the weighted space L(R+) ∩ H(R+) with the best choice of γ = 1 4 , some new and much better decay rates are further obtained: ‖∂ x(v− v̄)(t)‖L2 = O(1)(1 + t...

UCM1612+1308 is a new emission-line galaxy identified in the context of the Universidad Complutense de Madrid (UCM) survey. This object was classified as Blue Compact Galaxy (BCG) from photometric data. A detailed spectroscopic study fromnewoptical observations is presented now.The physical conditions and chemical composition are derived. The ionic abundances yield to a metallicity of 0.23 ± 0....

In the talk we will address the problem of finding an optimal dividend policy for a class of jumpdiffusion processes. The jump component is a compound Poisson process with negative jumps, and the drift and diffusion components are assumed to satisfy some regularity and growth restrictions. With each dividend payment there is associated a fixed and a proportional cost. The aim is to maximize exp...

We study off-shell effects of the pion cloud on the sea quark distribution in the nucleon. The structure function of the off-mass-shell pion is obtained within the Nambu and Jona-Lasinio model, where the shape of the distribution function depends on the pion momentum. By using the momentum dependent pion structure function, the SU(2) flavor asymmetry in the nucleon see is reexamined within the ...

To avoid un-realistic solutions like expansion shocks from appearing as a part of a solution it is necessary to satisfy the entropy condition for the Roe scheme. A variety of entropy fix formulae for the Roe scheme have been addressed in the literature. Three of the most famous are due to Harten-Hyman and Hoffmann-Chiang. These formulations have been assessed in this paper by applying them to t...