3,533 research outputs found
Consistency Condition for the Pinch Technique Self-Energies at Two Loops
A simple and testable necessary condition for the gauge independence of the
Pinch Technique self-energies at two loops is discussed. It is then shown that,
in the case of the and self-energies, the condition is indeed satisfied
by the Papavassiliou-Pilaftsis formulation.Comment: 7 pages, Latex, 1 PostScript figur
BRST-driven cancellations and gauge invariant Green's functions
We study a fundamental, all order cancellation operating between graphs of
distinct kinematic nature, which allows for the construction of
gauge-independent effective self-energies, vertices, and boxes at arbitrary
order.Comment: 4 pages, 3 figures. Contributed to QCD 03: High-Energy Physics
International Conference in Quantum Chromodynamics, Montpellier, France, 2-9
July 200
On the definition and observability of the neutrino charge radius
We present a brief summary of recent results concerning the unambiguous
definition and experimental extraction of the gauge-invariant and
process-independent neutrino charge radius.Comment: 5 pages, no figures, talk presented at the XXX International Meeting
on Fundamental Physics, IMFP2002, Jaca (Huesca), January 28th -- February
1st, 200
Gluon masses without seagull divergences
The study of dynamical gluon mass generation at the level of Schwinger-Dyson
equation involves a delicate interplay between various field-theoretic
mechanisms The underlying local gauge invariance remains intact by resorting to
the well-known Schwinger mechanism, which is assumed to be realized by
longitudinally coupled bound state poles, produced by the non-perturbative
dynamics of the theory. These poles are subsequently included into the
Schwinger-Dyson equation of the gluon propagator through the three-gluon
vertex, generating a non-vanishing gluon mass, which, however, is expressed in
terms of divergent seagull integrals. In this talk we explain how such
divergences can be eliminated completely by virtue of a characteristic
identity, valid in dimensional regularization. The ability to trigger this
identity depends, in turn, on the details of the three-gluon vertex employed,
and in particular, on the exact way the bound state poles are incorporated. A
concrete example of a vertex that triggers the aforementioned identity is
constructed, the ensuing cancellation of all seagull divergences is explicitly
demonstrated, and a finite gluon mass is obtained. Due to the multitude of
conditions that must be simultaneously satisfied, this construction appears to
be exclusively realized within the PT-BFM framework. The resulting system of
integral equations gives rise to a gluon mass that displays power-law running
and an effective charge which, due to the presence of the gluon mass, freezes
in the infrared at a finite (non-vanishing) value.Comment: 12 pages, 5 figures. Talk presented at the International Workshop on
QCD Green's Functions, Confinement, and Phenomenology - QCD-TNT09, September
07 - 11 2009, ECT* Trento, Ital
The Pinch Technique Approach to the Physics of Unstable Particles
The consistent description of unstable particles within the framework of
perturbative gauge field theories necessitates the definition and resummation
of off-shell Green's functions, which must respect several crucial physical
requirements. We present the solution to this problem at one-loop, using the
pinch technique.Comment: 11 pages, uses revtex, 7 Figures in separate ps file, contribution to
the 1998 Corfu Summer Institute on Elementary Particle Physics (JHEP
proceedings
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