1,645 research outputs found
The Glue Around Quarks and the Interquark Potential
The quarks of quark models cannot be identified with the quarks of the QCD
Lagrangian. We review the restrictions that gauge field theories place on any
description of physical (colour) charges. A method to construct charged
particles is presented. The solutions are applied to a variety of applications.
Their Green's functions are shown to be free of infra-red divergences to all
orders in perturbation theory. The interquark potential is analysed and it is
shown that the interaction responsible for anti-screening results from the
force between two separately gauge invariant constituent quarks. A fundamental
limit on the applicability of quark models is identified.Comment: 4 pages, LaTeX, talk given at Montpellier meeting QCD9
Asymptotic Dynamics in Quantum Field Theory
A crucial element of scattering theory and the LSZ reduction formula is the
assumption that the coupling vanishes at large times. This is known not to hold
for the theories of the Standard Model and in general such asymptotic dynamics
is not well understood. We give a description of asymptotic dynamics in field
theories which incorporates the important features of weak convergence and
physical boundary conditions. Applications to theories with three and four
point interactions are presented and the results are shown to be completely
consistent with the results of perturbation theory.Comment: 18 pages, 3 figure
The Structure of Screening in QED
The possibility of constructing charged particles in gauge theories has long
been the subject of debate. In the context of QED we have shown how to
construct operators which have a particle description. In this paper we further
support this programme by showing how the screening interactions arise between
these charges. Unexpectedly we see that there are two different gauge invariant
contributions with opposite signs. Their difference gives the expected result.Comment: 8 pages, LaTe
On the Significance of the Quantity "A Squared"
We consider the gauge potential A and argue that the minimum value of the
volume integral of A squared (in Euclidean space) may have physical meaning,
particularly in connection with the existence of topological structures. A
lattice simulation comparing compact and non-compact ``photodynamics'' shows a
jump in this quantity at the phase transition, supporting this idea.Comment: 6 pages, one figur
The factorisation of glue and mass terms in SU(N) gauge theories
In this paper we investigate the structure of the glue in Zwanziger's gauge
invariant expansion for the A^2-type mass term in Yang-Mills theory. We show
how to derive this expansion, in terms of the inverse covariant Laplacian, and
extend it to higher orders. In particular, we give an explicit expression, for
the first time, for the next to next to leading order term. We further show
that the expansion is not unique and give examples of the resulting ambiguity.Comment: 22 page
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