9 research outputs found
General Form of the Color Potential Produced by Color Charges of the Quark
Constant electric charge satisfies the continuity equation where is the current density of the electron.
However, the Yang-Mills color current density of the quark
satisfies the equation which is not a continuity
equation () which implies that a color charge
of the quark is not constant but it is time dependent where
are color indices. In this paper we derive general form of color
potential produced by color charges of the quark. We find that the general form
of the color potential produced by the color charges of the quark at rest is
given by \Phi^a(x) =A_0^a(t,{\bf x}) =\frac{q^b(t-\frac{r}{c})}{r}\[\frac{{\rm
exp}[g\int dr \frac{Q(t-\frac{r}{c})}{r}] -1}{g \int dr
\frac{Q(t-\frac{r}{c})}{r}}\]_{ab} where integration is an indefinite
integration, ~~ , ~~, ~~ is the retarded time, ~~ is the speed
of light, ~~ is the position of the quark at the retarded
time and the repeated color indices (=1,2,...8) are summed. For constant
color charge we reproduce the Coulomb-like potential
which is consistent with the Maxwell theory where
constant electric charge produces the Coulomb potential
.Comment: Final version, two more sections added, 45 pages latex, accepted for
publication in JHE
The role of the pion cloud in the interpretation of the valence light-cone wavefunction of the nucleon
The pion cloud renormalises the light-cone wavefunction of the nucleon which
is measured in hard, exclusive photon-nucleon reactions. We discuss the leading
twist contributions to high-energy exclusive reactions taking into account both
the pion cloud and perturbative QCD physics. The nucleon's electromagnetic
form-factor at high is proportional to the bare nucleon probability
and the cross-sections for hard (real at large angle or deeply virtual) Compton
scattering are proportional to . Our present knowledge of the pion-nucleon
system is consistent with . If we apply just perturbative QCD
to extract a light-cone wavefunction directly from these hard exclusive
cross-sections, then the light-cone wavefunction that we extract measures the
three valence quarks partially screened by the pion cloud of the nucleon. We
discuss how this pion cloud renormalisation effect might be understood at the
quark level in terms of the (in-)stability of the perturbative Dirac vacuum in
low energy QCD.Comment: Expanded Discussion of Phenomenology and Spin Physic