22 research outputs found
Condensation of vortices in the X-Y model in 3d: a disorder parameter
A disorder parameter is constructed which signals the condensation of
vortices. The construction is tested by numerical simulations.Comment: 9 pages, 5 postscript figures, typset using REVTE
More on ambiguities in the pole mass
The relation between the pole quark mass and the -renormalized
mass is governed by an infrared renormalon singularity, which leads to an
ambiguity of order in the definition of the pole mass. We use
the renormalization group and heavy quark effective theory to determine the
exact nature of this singularity up to an overall normalization. In the abelian
gauge theory, the normalization is computed partially to next-to-leading order
in the flavour expansion.Comment: LaTeX, 10 pages, Figures appended as uu-encoded file, UM-TH-94-3
Large-order Behaviour due to Ultraviolet Renormalons in QCD
Ultraviolet renormalons, contrary to their infrared counterparts, lead to a
universal contribution to the large-order behaviour of perturbative expansions
in QCD. In this letter, we determine nature of the leading ultraviolet
renormalon singularity for the inclusive hadroproduction cross section in annihilation, for hadronic decays and the moments of deep-inelastic
scattering structure functions. We comment on the relevance of ultraviolet
renormalons to estimates in low orders of perturbation theory.Comment: 9 pages, LaTe
An Order Parameter Reconciling Abelian and Center Dominance in SU(2) Yang-Mills Theory
We analyze previously proposed order parameters for the confinement -
deconfinement transition in lattice SU(2) Yang-Mills theory, defined as vacuum
expectation value (v.e.v.) of monopole fields in abelian projection gauges. We
show that they exhibit some inconsistency in the treatment of small scales, due
to a violation of Dirac quantization condition for fluxes. We propose a new
order parameter avoiding this inconsistency. It can be interpreted as v.e.v. of
the field of a regular monopole in any abelian projection gauge, but it is
independent of the choice of the abelian projection. Furthermore, being
constructed in terms of surfaces of center vortices, it has also a natural
interpretation in the approach of center dominance.Comment: TeX file, 31 page
Ultraviolet renormalons in abelian gauge theories
We analyze the large-order behaviour in perturbation theory of classes of
diagrams with an arbitrary number of chains (i.e. photon lines, dressed by
vacuum polarization insertions). We derive explicit formulae for the leading
and subleading divergence as , and a complete result for the vacuum
polarization at the next-to-leading order in . In general, diagrams with
more chains yield stronger divergence. We define an analogue of the familiar
diagrammatic -operation, which extracts ultraviolet renormalon counterterms
as insertions of higher-dimension operators. We then use renormalization group
equations to sum the leading -corrections to all orders in
and find the asymptotic behaviour in up to a constant that must be
calculated explicitly order by order in .Comment: 61 pages, LATEX, 10 figures as uu-decoded fil