21 research outputs found
Translation Invariance, Commutation Relations and Ultraviolet/Infrared Mixing
We show that the Ultraviolet/Infrared mixing of noncommutative field theories
with the Gronewold-Moyal product, whereby some (but not all) ultraviolet
divergences become infrared, is a generic feature of translationally invariant
associative products. We find, with an explicit calculation that the phase
appearing in the nonplanar diagrams is the one given by the commutator of the
coordinates, the semiclassical Poisson structure of the non commutative
spacetime. We do this with an explicit calculation for represented generic
products.Comment: 24 pages, 1 figur
Renormalisation of \phi^4-theory on noncommutative R^2 in the matrix base
As a first application of our renormalisation group approach to non-local
matrix models [hep-th/0305066], we prove (super-)renormalisability of Euclidean
two-dimensional noncommutative \phi^4-theory. It is widely believed that this
model is renormalisable in momentum space arguing that there would be
logarithmic UV/IR-divergences only. Although momentum space Feynman graphs can
indeed be computed to any loop order, the logarithmic UV/IR-divergence appears
in the renormalised two-point function -- a hint that the renormalisation is
not completed. In particular, it is impossible to define the squared mass as
the value of the two-point function at vanishing momentum. In contrast, in our
matrix approach the renormalised N-point functions are bounded everywhere and
nevertheless rely on adjusting the mass only. We achieve this by introducing
into the cut-off model a translation-invariance breaking regulator which is
scaled to zero with the removal of the cut-off. The naive treatment without
regulator would not lead to a renormalised theory.Comment: 26 pages, 44 figures, LaTe
Star Product and Invariant Integration for Lie type Noncommutative Spacetimes
We present a star product for noncommutative spaces of Lie type, including
the so called ``canonical'' case by introducing a central generator, which is
compatible with translations and admits a simple, manageable definition of an
invariant integral. A quasi-cyclicity property for the latter is shown to hold,
which reduces to exact cyclicity when the adjoint representation of the
underlying Lie algebra is traceless. Several explicit examples illuminate the
formalism, dealing with kappa-Minkowski spacetime and the Heisenberg algebra
(``canonical'' noncommutative 2-plane).Comment: 21 page
Euclidean Configuration Space Renormalization, Residues and Dilation Anomaly1
Configuration (x-)space renormalization of euclidean Feynman amplitudes in a massless quantum field theory is reduced to the study of local extensions of associate homogeneous distributions. Primitively divergent graphs are renormalized, in particular, by subtracting the residue of an analytically regularized expression. Examples are given of computing residues that involve zeta values. The renormalized Green functions are again associate homogeneous distributions of the same degree that transform under indecomposable representations of the dilation group
Degenerate noncommutativity
We study a renormalizable four dimensional model with two deformed quantized
space directions. A one-loop renormalization is performed explicitly. The
Euclidean model is connected to the Minkowski version via an analytic
continuation. At a special value of the parameters a nontrivial fixed point of
the renormalization group occurs.Comment: 16 page
Pair Production of Neutral Higgs Bosons through Noncommutative QED Interactions at Linear Colliders
We study the feasibility of detecting noncommutative (NC) QED through neutral
Higgs boson (H) pair production at linear colliders (LC). This is based on the
assumption that H interacts directly with photon in NCQED as suggested by
symmetry considerations and strongly hinted by our previous study on
\pi^0-photon interactions. We find the following striking features as compared
to the standard model (SM) result: (1) generally larger cross sections for an
NC scale of order 1 TeV; (2) completely different dependence on initial beam
polarizations; (3) distinct distributions in the polar and azimuthal angles;
and (4) day-night asymmetry due to the Earth's rotation. These will help to
separate NC signals from those in the SM or other new physics at LC. We
emphasize the importance of treating properly the Lorentz noninvariance problem
and show how the impact of the Earth's rotation can be used as an advantage for
our purpose of searching for NC signals.Comment: 12 pages, 3 figures using axodraw.sty; v2: proof version in Phys.
Rev. D, minor rewordin
Anomaly freedom in Seiberg-Witten noncommutative gauge theories
We show that noncommutative gauge theories with arbitrary compact gauge group
defined by means of the Seiberg-Witten map have the same one-loop anomalies as
their commutative counterparts. This is done in two steps. By explicitly
calculating the \epsilon^{\m_1\m_2\m_3\m_4} part of the renormalized
effective action, we first find the would-be one-loop anomaly of the theory to
all orders in the noncommutativity parameter \theta^{\m\n}. And secondly we
isolate in the would-be anomaly radiative corrections which are not BRS
trivial. This gives as the only true anomaly occurring in the theory the
standard Bardeen anomaly of commutative spacetime, which is set to zero by the
usual anomaly cancellation condition.Comment: LaTeX 2e, no macros, no figures, 32 A4 page
Noncommutative vector bundles over fuzzy CP^N and their covariant derivatives
We generalise the construction of fuzzy CP^N in a manner that allows us to
access all noncommutative equivariant complex vector bundles over this space.
We give a simplified construction of polarization tensors on S^2 that
generalizes to complex projective space, identify Laplacians and natural
noncommutative covariant derivative operators that map between the modules that
describe noncommuative sections. In the process we find a natural
generalization of the Schwinger-Jordan construction to su(n) and identify
composite oscillators that obey a Heisenberg algebra on an appropriate Fock
space.Comment: 34 pages, v2 contains minor corrections to the published versio
Star products made (somewhat) easier
We develop an approach to the deformation quantization on the real plane with
an arbitrary Poisson structure which based on Weyl symmetrically ordered
operator products. By using a polydifferential representation for deformed
coordinates we are able to formulate a simple and effective
iterative procedure which allowed us to calculate the fourth order star product
(and may be extended to the fifth order at the expense of tedious but otherwise
straightforward calculations). Modulo some cohomology issues which we do not
consider here, the method gives an explicit and physics-friendly description of
the star products.Comment: 20 pages, v2, v3: comments and references adde