49 research outputs found
Time ordered perturbation theory for non-local interactions; applications to NCQFT
In the past decades, time ordered perturbation theory was very successful in
describing relativistic scattering processes. It was developed for local
quantum field theories. However, there are field theories which are governed by
non-local interactions, for example non-commutative quantum field theory
(NCQFT). Filk (Phys. Lett. B 376 (1996) 53) first studied NCQFT perturbatively
obtaining the usual Feynman propagator and additional phase factors as the
basic elements of perturbation theory. However, this treatment is only
applicable for cases, where the deformation of space-time does not involve
time. Thus, we generalize Filk's approach in two ways: First, we study
non-local interactions of a very general type able to embed NCQFT. And second,
we also include the case, where non-locality involves time. A few applications
of the obtained formalism will also be discussed.Comment: 21 pages, 2 figure
A Vector Supersymmetry Killing the Infrared Singularity of Gauge Theories in Noncommutative Space
We show that the "topological BF-type" term introduced by Slavnov in order to
cure the infrared divergences of gauge theories in noncommutative space can be
characterized as the consequence of a new symmetry. This symmetry is a
supersymmetry, generated by vector charges, of the same type as the one
encountered in Chern-Simons or BF topological theories.Comment: 9 pages, LaTex. Work presented by O. Piguet at the Fifth
International Conference on Mathematical Methods in Physics, 24 - 28 April
2006, Rio de Janeiro, Brazi
The Energy-Momentum Tensor(s) in Classical Gauge Theories
We give an introduction to, and review of, the energy-momentum tensors in
classical gauge field theories in Minkowski space, and to some extent also in
curved space-time. For the canonical energy-momentum tensor of non-Abelian
gauge fields and of matter fields coupled to such fields, we present a new and
simple improvement procedure based on gauge invariance for constructing a gauge
invariant, symmetric energy-momentum tensor. The relationship with the
Einstein-Hilbert tensor following from the coupling to a gravitational field is
also discussed.Comment: 34 pages; v2: Slightly expanded version with some improvements of
presentation; Contribution to Mathematical Foundations of Quantum Field
Theory, special issue in memory of Raymond Stora, Nucl. Phys.
Renormalization of the noncommutative photon self-energy to all orders via Seiberg-Witten map
We show that the photon self-energy in quantum electrodynamics on
noncommutative is renormalizable to all orders (both in
and ) when using the Seiberg-Witten map. This is due to the enormous
freedom in the Seiberg-Witten map which represents field redefinitions and
generates all those gauge invariant terms in the -deformed classical
action which are necessary to compensate the divergences coming from loop
integrations.Comment: 12 pages, LaTeX2e. v3: added references, changed title. The general
renormalizability proof for noncommutative Maxwell theory turned out to be
incomplete, therefore, we have to restrict the proof to the noncommutative
photon self-energ
No parity anomaly in massless QED3: a BPHZL approach
In this letter we call into question the perturbatively parity breakdown at
1-loop for the massless QED_3 frequently claimed in the literature. As long as
perturbative quantum field theory is concerned, whether a parity anomaly owing
to radiative corrections exists or not will be definitely proved by using a
renormalization method independent of any regularization scheme. Such a problem
has been investigated in the framework of BPHZL renormalization method, by
adopting the Lowenstein-Zimmermann subtraction scheme. The 1-loop parity-odd
contribution to the vacuum-polarization tensor is explicitly computed in the
framework of the BPHZL renormalization method. It is shown that a Chern-Simons
term is generated at that order induced through the infrared subtractions --
which violate parity. We show then that, what is called parity anomaly, is in
fact a parity-odd counterterm needed for restauring parity.Comment: 4 pages, no figures, to appear in Physics Letters