423 research outputs found
The shuffle Hopf algebra and quasiplanar Wick products
The operator valued distributions which arise in quantum field theory on the
noncommutative Minkowski space can be symbolized by a generalization of chord
diagrams, the dotted chord diagrams. In this framework, the combinatorial
aspects of quasiplanar Wick products are understood in terms of the shuffle
Hopf algebra of dotted chord diagrams, leading to an algebraic characterization
of quasiplanar Wick products as a convolution. Moreover, it is shown that the
distributions do not provide a weight system for universal knot invariants.Comment: 16 pages, prepared for the conference proceedings "Non commutative
Geometry and Physics", Laboratoire de physique th\'eorique d'Orsay, April
23-27, 200
Unitary Quantum Field Theory on the Noncommutative Minkowski space
This is the written version of a talk I gave at the 35th Symposium Ahrenshoop
in Berlin, Germany, August 2002. It is an exposition of joint work with S.
Doplicher, K. Fredenhagen, and Gh. Piacitelli [1]. The violation of unitarity
found in quantum field theory on noncommutative spacetimes in the context of
the so-called modified Feynman rules is linked to the notion of time ordering
implicitely used in the assumption that perturbation theory may be done in
terms of Feynman propagators. Two alternative approaches which do not entail a
violation of unitarity are sketched. An outlook upon our more recent work is
given.Comment: 6 pages. To appear in the proceedings of 35th International Symposium
Ahrenshoop on the theory of Elementary Particles: Recent Developments in
String / M Theory and Field Theory, Berlin, Germany, 26-30 Aug 2002 (special
issue of the journal "Fortschritte der Physik") v2: minor addition to the
abstrac
No UV/IR Mixing in Unitary Space-Time Noncommutative Field Theory
In this article we calculate several divergent amplitudes in phi^4-theory on
non-commutative space-time in the framework of Interaction Point Time Ordered
Perturbation Theory (IPTOPT), continuing work done in hep-th/0209253. On the
ground of these results we find corresponding Feynman rules which allow for a
much easier diagrammatic calculation of amplitudes. The most important feature
of the present theory is the lack of the UV/IR mixing problem in all amplitudes
calculated so far. Although we are not yet able to give a rigorous proof, we
provide a strong argument for this result to hold in general. Together with the
found Feynman rules this opens promising vistas towards the systematic
renormalization of non-commutative field theories.Comment: 23 pages, uses package feynmf, v2: typos, added reference, minor
improvement
UV Finite Field Theories on Noncommutative Spacetimes: the Quantum Wick Product and Time Independent Perturbation Theory
In this article an energy correction is calculated in the time independent
perturbation setup using a regularised ultraviolet finite Hamiltonian on the
noncommutative Minkowski space. The correction to the energy is invariant under
rotation and translation but is not Lorentz covariant and this leads to a
distortion of the dispersion relation. In the limit where the noncommutativity
vanishes the common quantum field theory on the commutative Minkowski space is
reobtained.Comment: 8 pages, 2 figure
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