DISTORTIONS IN THE NEGATIVE ENERGY DIRAC SEA: VIOLATION OF THE GOTTFRIED SUM RULE AND $\Delta \bar u$ 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 $\Delta\bar{d}$.