Simple formulas on ∆d̄(x)−∆ū(x) are proposed for extracting their values from polarized deep-inelastic semiinclusive data. The present SMC and HERMES data suggest that ∆d̄(x)−∆ū(x) is slightly negative, though the precision of the data is not enough for confirming it.

We study the d̄− ū asymmetry of the proton in a model approach in which hadronic fluctuations of the nucleon are generated through gluon splitting and recombination mechanisms. Within this framework, it is shown that the d̄ − ū asymmetry of the proton is consistently described by including only nucleon fluctuations to |πN〉 and |π∆〉 bound states. Predictions of the model closely agree with the rec...

This paper presents a potentially powerful canonical dual transformation method and associated duality theory for solving fully nonlinear distributed-parameter control problems. The extended Lagrange duality and the interesting triality theory proposed recently in finite deformation theory are generalized into nonconvex dynamical systems. A bifurcation criterion is proposed, which leads to an e...

A phenomenological ansatz for the flavor–asymmetry of the light sea distributions of the nucleon, based on the Pauli exclusion principle, is proposed. This ansatz is compatible with the measured flavor–asymmetry of the unpolarized sea distributions, d̄ > ū, of the nucleon. A prediction for the corresponding polarized flavor–asymmetry is presented and shown to agree with predictions of (chiral qu...

Various shadowing aspects of nuclear parton distributions are discussed in a partonmodel framework. We explain existing x dependent data of F 2 /F 2 , then the model is applied to a flavor asymmetry ū − d̄ in a nucleus, to shadowing in valence-quark distributions, and to nuclear dependence of Q evolution. First, we find that a finite nuclear ū−d̄ distribution could be possible due to nuclear inte...

We study the normalized difference between the solution u of a reaction–diffusion equation in a bounded interval [0,L], perturbed by a fast oscillating term arising as the solution of a stochastic reaction–diffusion equation with a strong mixing behavior, and the solution ū of the corresponding averaged equation. We assume the smoothness of the reaction coefficient and we prove that a central l...

As in the classical paper of Lax [L], we assume here that the system is strictly hyperbolic with each characteristic field either linearly degenerate or genuinely nonlinear. In this setting, the recent progress in the field has shown that within the class of initial data ū ∈ L ∩BV (R,R) having the total variation suitably small, the problem (1.1) (1.2) is well posed in L(R,R). Namely, as proved...

We present a calculation of the polarized ρ meson cloud in a nucleon using time-ordered perturbation theory in two different variants advocated in the literature. We calculate the induced difference between the distributions ∆d̄(x) and ∆ū(x). We use a recent lattice calculation to motivate an ansatz for the polarized valence quark distribution of the ρ meson. Our calculations show that the two t...

SU(2)-flavor-symmetry breaking in antiquark distributions of the nucleon was suggested by the New Muon Collaboration (NMC) in deep inelastic muon scattering. As an independent test, Drell-Yan data for the tungsten target have been used for examining the asymmetry. We investigate whether there exists significant modification of the ū− d̄ distribution in nuclei in a parton recombination model. It ...

We study the singular ordinary differential equation dU dt = 1 ζ(U) φs(U) + φns(U), (0.1) where U ∈ R , the functions φs ∈ R N and φns ∈ R N are of class C and ζ is a real valued C function. The equation is singular in the sense that ζ(U) can attain the value 0. We focus on the solutions of (0.1) that belong to a small neighbourhood of a point Ū such that φs(Ū) = φns(Ū) = ~0, ζ(Ū) = 0. We inves...