Distortions in the negative energy Dirac sea: Violation of the Gottfried sum rule and Du in the proton

Abstract

We report on recent work concerning the effect which the change in vacuum structure (negative energy Dirac sea), in the presence of a confining scalar field, has on the nucleon structure functions and parton distributions. Using the Dirac equation in 1+1 dimensions, we show that distortions in the Dirac sea are responsible for part of the violation of the Gottfried sum rule -- i.e., part of the flavor asymmetry in the proton sea. Our basic argument is that, even if isospin is an exact symmetry, the presence of a confining potential changes the vacuum structure, and inevitably leads to a violation of SU(2) flavour symmetry in a hadron with a different number of valence $u$ and $d$ quarks. The same mechanism also leads to a prediction for $\Delta\bar{u}$ and $\Delta\bar{d}$.