369 research outputs found
Translational-invariant noncommutative gauge theory
A generalized translational invariant noncommutative field theory is analyzed
in detail, and a complete description of translational invariant noncommutative
structures is worked out. The relevant gauge theory is described, and the
planar and nonplanar axial anomalies are obtained.Comment: V1: 23 pages, 4 figures; V2: Section I. improved, References added.
Version accepted for publication in PR
Gauge Invariant Cutoff QED
A hidden generalized gauge symmetry of a cutoff QED is used to show the
renormalizability of QED. In particular, it is shown that corresponding Ward
identities are valid all along the renormalization group flow. The exact
Renormalization Group flow equation corresponding to the effective action of a
cutoff lambda phi^4 theory is also derived. Generalization to any gauge group
is indicated.Comment: V1: 18 pages, 2 figures; V2: Discussions improved. Version accepted
for publication in Physica Script
Cyanobacterial community patterns as water quality bioindicators
The main goal of this study was to examine the use of cyanobacteria for evaluating the quality of running water. Accordingly epilithic cyanobacterial communities were collected in Dez River and Ojeyreb drain in south of Iran. Samples were collected in two seasons: autumn and spring. Effective physical and chemical factors on the structure of cyanobacterial communities and the dispersion of the species in relation with them were determined using PCA and CCA analyses. The Shannon-Wiener biodiversity index was used to define the species diversity. The concentration of nitrate as main nutrient had significant increase in Drain stations. A decline in species richness was observed associated with these increases in nutrient load in both seasons in different cyanobacterial community structure. The results indicated that order Oscillatoriales had higher proportion of cyanobacteria species at Drain. The species Oscillatoria chlorina, Chroococcus minor, Phormidium tenue and Lyngbya kuetzingii S had the most positive correlation with nutrient factor. Species Lyngbya infixa and Lyngbya mesotrichia had the most negative correlation with nitrate. Our results confirm the using of cyanobacteria species as indicators for monitoring eutrophication in rivers and define them as water eutrophication bioindicators
Testing Spatial Noncommutativity via Rydberg Atoms
The possibility of testing spatial noncommutativity via Rydberg atoms is
explored. An atomic dipole of a cold Rydberg atom is arranged in appropriate
electric and magnetic field, so that the motion of the dipole is constrained to
be planar and rotationally symmetric. Spatial noncommutativity leads to that
the canonical angular momentum possesses fractional values. In the limit of
vanishing kinetic energy, the dominate value of the lowest canonical angular
momentum takes . Furthermore, in the limit of eliminating magnetic
field, the dominate value of the lowest canonical angular momentum changes from
to . This result is a clear signal of spatial
noncommutativity. An experimental verification of this prediction is suggested.Comment: 10 pages. Physical Review Letters (in press
Non-commutative holography and scattering amplitudes in a large magnetic background
We study planar gluon scattering amplitudes and Wilson loops in
non-commutative gauge theory. Our main results are:
1. We find the map between observables in non-commutative gauge theory and
their holographic dual. In that map, the region near the boundary of the
gravitational dual describes the physics in terms of T-dual variables.
2. We show that in the presence of a large magnetic background and a UV
regulator, a planar gluon scattering amplitude reduces to a complex polygon
Wilson loop expectation value, dressed by a tractable polarization dependent
factor.Comment: 26 pages. v2: corrected section 4, reference adde
BRST Quantization of Noncommutative Gauge Theories
In this paper, the BRST symmetry transformation is presented for the
noncommutative U(N) gauge theory. The nilpotency of the charge associated to
this symmetry is then proved. As a consequence for the space-like
non-commutativity parameter, the Hilbert space of physical states is determined
by the cohomology space of the BRST operator as in the commutative case.
Further, the unitarity of the S-matrix elements projected onto the subspace of
physical states is deduced.Comment: 20 pages, LaTeX, no figures, one reference added, to appear in Phys.
Rev.
A note on bosonic open strings in constant B field
We sketch the main steps of old covariant quantization of bosonic open
strings in a constant field background. We comment on its space-time
symmetries and the induced effective metric. The low-energy spectrum is
evaluated and the appearance of a new non-commutative gauge symmetry is
addressed.Comment: 13 pages, Latex, important comments added, to appear in PR
Planar and Nonplanar Konishi Anomalies and Effective Superpotential for Noncommutative N=1 Supersymmetric U(1)
The Konishi anomalies for noncommutative N=1 supersymmetric U(1) gauge theory
arising from planar and nonplanar diagrams are calculated. Whereas planar
Konishi anomaly is the expected \star-deformation of the commutative anomaly,
nonplanar anomaly reflects the important features of nonplanar diagrams of
noncommutative gauge theories, such as UV/IR mixing and the appearance of
nonlocal open Wilson lines. We use the planar and nonplanar Konishi anomalies
to calculate the effective superpotential of the theory. In the limit of
vanishing |\Theta p|, with \Theta the noncommutativity parameter, the
noncommutative effective superpotential depends on a gauge invariant
superfield, which includes supersymmetric Wilson lines, and has nontrivial
dependence on the gauge field supermultiplet.Comment: LaTeX, 36 pages. Version 2: Typos Corrected. Version 3: Extensively
revised version, 42 pages, to be published in Int. J. Mod. Phys. A. (2005
Commutator Anomaly in Noncommutative Quantum Mechanics
In this letter, firstly, the Schrdinger equation on noncommutative
phase space is given by using a generalized Bopp's shift. Then the anomaly term
of commutator of arbitrary physical observable operators on noncommutative
phase space is obtained. Finally, the basic uncertainty relations for
space-space and space-momentum as well as momentum-momentum operators in
noncommutative quantum mechanics (NCQM), and uncertainty relation for arbitrary
physical observable operators in NCQM are discussed.Comment: 7 page
Investigation of antioxidant activity of nonpolar and semipolar natural compounds of the Persian Gulf Sea Cucumber (Holothuria sp.)by using Oil Stability Index (OSI) method
In this investigation, nonpolar and semipolar compounds in sea cucumber (Holothuria sp.) collected from coasts of Lengeh Port were extracted by Bligh &Dyer method. The extraction of nonpolar and semipolar natural compounds was conducted by Hexane and Ether, respectively. After condensation, the prepared samples were injected into gas chromatography machine equipped with mass spectroscopy; and mass spectra obtained, using Eight Peak reference, and Kuats index (KI) and its conformity with standard Kuats index was also assessed. The compounds in Hexane-Ether phases were identified. Based on the results, in the Hexane phase of sea cucumber issue, there were nine compounds including: 2-Octanol (5.23 %), 5-Methyl 2-Hexanol (8.05 %), 2-Nonanol (2.5%), Cyclohexasiloxane, Dodecamethyl (2.09%), 3-Hydroxystearic (1.66%), Methyl Arachidonate (20.65%), 1, 4, 8, Dodecatriene (21.71%), Oleicacid (30.27%), and 1-Dodecanol (2.52%). There were also seven compounds in the Ether phase including: Tetradecane (0.63%), Palmitoleic acid (1.23%), Palmitic acid (1.63%), Oleic acid (40.31%), Stearic acid (3.40%), Methyl Arachidonate (28.62%), and 1, 2- Benzendicarboxlic acid (2-ethyl hexyl) (2.71%). We found that in both phases the main ingredient is Oleic acid. The investigation of antioxidant activity was conducted by the OSI and Rancimat apparatus. We detected no antioxidant activity in the sea cucumber compounds
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