The flavor asymmetry of the polarized light sea, ∆ū −∆d̄, discriminates between different model calculations of helicity densities. We show that the chiral chromodielectric model, differently from models based on a 1/Nc expansion, predicts a small value for this asymmetry, what seems in agreement with preliminary HERMES data. 1. Following the discovery that the quark contribution to the spin of ...

We examine the space-time properties of the distributions of (d̄− ū) and d̄/ū in the proton. The difference of the antiquark distributions shows the expected peak at the approximate pion Compton wavelength and is supportive of the thesis that the meson cloud of the nucleon is at the origin of the asymmetry of (d̄ − ū), with the pion cloud playing a dominant role. The partonic distribution function...

We study the possible flavour asymmetry, ū 6= d̄, of the light quark sea distributions of the proton. We discuss the information that is at present available from data on deep-inelastic lepton-nucleon scattering and from DrellYan production on various nuclear targets. We show that the ratio of dilepton yields on hydrogen and deuterium targets is very sensitive to ū − d̄. The increased precision o...

Theoretical predictions are given for the light-flavor sea-quark distributions including the strange quark ones on the basis of the flavor SU(3) version of the chiral quark soliton model. Careful account is taken here of the SU(3) symmetry breaking effects due to the mass difference between the strange and nonstrange quarks. This effective mass difference ∆ms between the strange and nonstrange ...

Flavor asymmetry in the light quark sea of the proton has been well-established by experiment [1–4]. The violation of the Gottfried sum rule found by NMC [1] indicated that D ≡ ∫ 1 0 dx (d̄(x) − ū(x)) = 0.148 ± 0.039. In Drell-Yan experiments, d̄/ū was determined to be greater than 2 at x = .18 by NA51 [2], and the x-dependence of this ratio has recently been measured by E866 [3] in the region 0....

This paper is devoted to second order necessary optimality conditions for the Mayer optimal control problem when the control set U is a closed subset of R. We show that, in the absence of endpoint constraints, if an optimal control ū(·) is singular and integrable, then for almost every t such that ū(t) is in the interior of U , both the Goh and a generalized LegendreClebsch conditions hold true...

Abstract This paper provides a new explanation for the insertion of * in plural forms CVCC- nouns also formed with an external suffix, e.g. ʕabd- : ʕabad-ū- ‘servant(s)’, various Semitic languages. CVCaC-ū- pattern is usually considered to be remnant Proto-Semitic broken system Northwest Semitic, but we show that it goes back this form. Internal evidence from as well comparative Afroasiatic poi...

Abstract. The unipotent variety of a reductive algebraic group G plays an important role in the representation theory. In this paper, we will consider the closure Ū of the unipotent variety in the De Concini-Procesi compactification Ḡ of a quasisimple, adjoint group G. We will prove that Ū − U is a union of some G-stable pieces introduced by Lusztig in [L4]. This was first conjectured by Luszti...