6 research outputs found
On Non-Commutative U*(1) Gauge Models and Renormalizability
Based on our recent findings regarding (non-)renormalizability of
non-commutative U*(1) gauge theories [arxiv:0908.0467, arxiv:0908.1743] we
present the construction of a new type of model. By introducing a soft breaking
term in such a way that only the bilinear part of the action is modified, no
interaction between the gauge sector and auxiliary fields occurs. Demanding in
addition that the latter form BRST doublet structures, this leads to a
minimally altered non-commutative U*(1) gauge model featuring an IR damping
behavior. Moreover, the new breaking term is shown to provide the necessary
structure in order to absorb the inevitable quadratic IR divergences appearing
at one-loop level in theories of this kind. In the present paper we compute
Feynman rules, symmetries and results for the vacuum polarization together with
the one-loop renormalization of the gauge boson propagator and the three-point
functions.Comment: 20 pages, 4 figures; v2-v4: clarified several points, and minor
correction
On the Renormalizability of Noncommutative U(1) Gauge Theory - an Algebraic Approach
We investigate the quantum effects of the nonlocal gauge invariant operator
in the
noncommutative U(1) action and its consequences to the infrared sector of the
theory. Nonlocal operators of such kind were proposed to solve the infrared
problem of the noncommutative gauge theories evading the questions on the
explicit breaking of the Lorentz invariance. More recently, a first step in the
localization of this operator was accomplished by means of the introduction of
an extra tensorial matter field, and the first loop analysis was carried out
. We will complete this localization
avoiding the introduction of new degrees of freedom beyond those of the
original action by using only BRST doublets. This will allow us to make a
complete BRST algebraic study of the renormalizability of the theory, following
Zwanziger's method of localization of nonlocal operators in QFT.Comment: standard Latex no figures, version2 accepted in J. Phys A: Math Theo
A New Approach to Non-Commutative U(N) Gauge Fields
Based on the recently introduced model of arXiv:0912.2634 for non-commutative
U(1) gauge fields, a generalized version of that action for U(N) gauge fields
is put forward. In this approach to non-commutative gauge field theories, UV/IR
mixing effects are circumvented by introducing additional 'soft breaking' terms
in the action which implement an IR damping mechanism. The techniques used are
similar to those of the well-known Gribov-Zwanziger approach to QCD.Comment: 11 pages; v2 minor correction
One-Loop Calculations for a Translation Invariant Non-Commutative Gauge Model
In this paper we discuss one-loop results for the translation invariant
non-commutative gauge field model we recently introduced in arXiv:0804.1914.
This model relies on the addition of some carefully chosen extra terms in the
action which mix long and short scales in order to circumvent the infamous
UV/IR mixing, and were motivated by the renormalizable non-commutative scalar
model of Gurau et al. (cf. arXiv:0802.0791).Comment: 18 pages, v2: minor correction
Conservative drug treatment in patients with moderately severe chronic occlusive peripheral arterial disease. Scandinavian Study Group.
Unveiling distribution patterns of freshwater phytoplankton by a next generation sequencing based approach
The recognition and discrimination of phytoplankton species is one of the foundations of freshwater biodiversity research and environmental monitoring. This step is frequently a bottleneck in the analytical chain from sampling to data analysis and subsequent environmental status evaluation. Here we present phytoplankton diversity data from 49 lakes including three seasonal surveys assessed by next generation sequencing (NGS) of 16S ribosomal RNA chloroplast and cyanobacterial gene amplicons and also compare part of these datasets with identification based on morphology. Direct comparison of NGS to microscopic data from three time-series showed that NGS was able to capture the seasonality in phytoplankton succession as observed by microscopy. Still, the PCR-based approach was only semi-quantitative, and detailed NGS and microscopy taxa lists had only low taxonomic correspondence. This is probably due to, both, methodological constraints and current discrepancies in taxonomic frameworks. Discrepancies included Euglenophyta and Heterokonta that were scarce in the NGS but frequently detected by microscopy and Cyanobacteria that were in general more abundant and classified with high resolution by NGS. A deep-branching taxonomically unclassified cluster was frequently detected by NGS but could not be linked to any group identified by microscopy. NGS derived phytoplankton composition differed significantly among lakes with different trophic status, showing that our approach can resolve phytoplankton communities at a level relevant for ecosystem management. The high reproducibility and potential for standardization and parallelization makes our NGS approach an excellent candidate for simultaneous monitoring of prokaryotic and eukaryotic phytoplankton in inland waters.peerReviewe