229 research outputs found
Gauge field theories with covariant star-product
A noncommutative gauge theory is developed using a covariant star-product
between differential forms defined on a symplectic manifold, considered as the
space-time. It is proven that the field strength two-form is gauge covariant
and satisfies a deformed Bianchi identity. The noncommutative Yang-Mills action
is defined using a gauge covariant metric on the space-time and its gauge
invariance is proven up to the second order in the noncommutativity parameter.Comment: Dedicated to Ioan Gottlieb on the occasion of his 80th birthday
anniversary. 12 page
Quantum Field Theory on the Noncommutative Plane with Symmetry
We study properties of a scalar quantum field theory on the two-dimensional
noncommutative plane with quantum symmetry. We start from the
consideration of a firstly quantized quantum particle on the noncommutative
plane. Then we define quantum fields depending on noncommutative coordinates
and construct a field theoretical action using the -invariant measure
on the noncommutative plane. With the help of the partial wave decomposition we
show that this quantum field theory can be considered as a second quantization
of the particle theory on the noncommutative plane and that this field theory
has (contrary to the common belief) even more severe ultraviolet divergences
than its counterpart on the usual commutative plane. Finally, we introduce the
symmetry transformations of physical states on noncommutative spaces and
discuss them in detail for the case of the quantum group.Comment: LaTeX, 26 page
Aharonov-Casher effect for spin one particles in a noncommutative space
In this work the Aharonov-Casher (AC) phase is calculated for spin one
particles in a noncommutative space. The AC phase has previously been
calculated from the Dirac equation in a noncommutative space using a gauge-like
technique [17]. In the spin-one, we use kemmer equation to calculate the phase
in a similar manner. It is shown that the holonomy receives non-trivial
kinematical corrections. By comparing the new result with the already known
spin 1/2 case, one may conjecture a generalized formula for the corrections to
holonomy for higher spins.Comment: 9 page
Noncommutative BTZ Black Hole in Polar Coordinates
Based on the equivalence between the three dimensional gravity and the
Chern-Simons theory, we obtain a noncommutative BTZ black hole solution as a
solution of noncommutative Chern-Simons theory using the
Seiberg-Witten map. The Seiberg-Witten map is carried out in a noncommutative
polar coordinates whose commutation relation is equivalent to the usual
canonical commutation relation in the rectangular coordinates up to first order
in the noncommutativity parameter . The solution exhibits a
characteristic of noncommutative polar coordinates in such a way that the
apparent horizon and the Killing horizon coincide only in the non-rotating
limit showing the effect of noncommutativity between the radial and angular
coordinates.Comment: 14 pages, V2: minor changes, v3: reduced for clarification, a
reference adde
The topological AC effect on noncommutative phase space
The Aharonov-Casher (AC) effect in non-commutative(NC) quantum mechanics is
studied. Instead of using the star product method, we use a generalization of
Bopp's shift method. After solving the Dirac equations both on noncommutative
space and noncommutative phase space by the new method, we obtain the
corrections to AC phase on NC space and NC phase space respectively.Comment: 8 pages, Latex fil
and colliding in noncommutative space
By studying the scattering process of scalar particle pion on the
noncommutative scalar quantum electrodynamics, the non-commutative amendment of
differential scattering cross-section is found, which is dependent of
polar-angle and the results are significantly different from that in the
commutative scalar quantum electrodynamics, particularly when . The non-commutativity of space is expected to be explored at around
TeV.Comment: Latex, 12 page
Prevalence of vitamin d deficiency amongwomen of reproductive age: A multi centric study in tehran
Background and Objectives: The aim of this study was to determine the prevalence of vitaminDdeficiency among Iranianwomenof reproductive age. Methods: In this multicentric cross-sectional study, 300 women aged 15 - 45 years referring to Tehran branch of Islamic Azad university hospitals from 2013 to 2015 were recruited. The collected data included the demographic characteristics of the participants, including age, body mass index (BMI), parity, and serum level of vitamin D. Serum levels of 25-dihydroxy vitamin D were measured by radioimmunoassay. Vitamin D was defined as deficient < 20 nmol/L, mild 25 nmol/L, moderate 12.5 - 25 nmol/L and severe12.5 nmol/L. Statistical analysis was performed, using Excel software. Results: Amongthe300patients, 257 caseshadvitaminDdeficiency;amongwhom,122 caseshadsevere, 96hadmoderateand38hadmild deficiency. Conclusions: According to the results of this study, only 14.8 of the study population had normal serum vitamin D levels, indicating that the majority of Iranian women in the reproductive age have vitamin D deficiency. © 2016, Shiraz University of Medical Sciences
Non-Commutativity and Unitarity Violation in Gauge Boson Scattering
We examine the unitarity properties of spontaneously broken non-commutative
gauge theories. We find that the symmetry breaking mechanism in the
non-commutative Standard Model of Chaichian et al. leads to an unavoidable
violation of tree-level unitarity in gauge boson scattering at high energies.
We then study a variety of simplified spontaneously broken non-commutative
theories and isolate the source of this unitarity violation. Given the group
theoretic restrictions endemic to non-commutative model building, we conclude
that it is difficult to build a non-commutative Standard Model under the
Weyl-Moyal approach that preserves unitarity.Comment: 31 page
Deformations of the Boson Representation and its Subalgebras
The boson representation of the sp(4,R) algebra and two distinct deformations
of it, are considered, as well as the compact and noncompact subalgebras of
each. The initial as well as the deformed representations act in the same Fock
space.
One of the deformed representation is based on the standard q-deformation of
the boson creation and annihilation operators. The subalgebras of sp(4,R)
(compact u(2) and three representations of the noncompact u(1,1) are also
deformed and are contained in this deformed algebra. They are reducible in the
action spaces of sp(4,R) and decompose into irreducible representations.
The other deformed representation, is realized by means of a transformation
of the q-deformed bosons into q-tensors (spinor-like) with respect to the
standard deformed su(2). All of its generators are deformed and have
expressions in terms of tensor products of spinor-like operators. In this case,
an other deformation of su(2) appears in a natural way as a subalgebra and can
be interpreted as a deformation of the angular momentum algebra so(3). Its
representation is reducible and decomposes into irreducible ones that yields a
complete description of the same
Noncommutative Dirac oscillator in an external magnetic field
We show that (2+1) dimensional noncommutative Dirac oscillator in an external
magnetic field is mapped onto the same but with reduced angular frequency in
absence of magnetic field. We construct the relativistic Landau levels by
solving corresponding Dirac equation in (2+1) dimensional noncommutative phase
space. We observe that lowest Landau levels are exactly same as in commutative
space and independent of non-commutative parameter. All the Landau levels
become independent of noncommutative parameter for a critical value of the
magnetic field. Several other interesting features along with the relevance of
such models in the study of atomic transitions in a radiation field have been
discussed.Comment: 10 pages, Np figs, communicated to journal. arXiv admin note: text
overlap with arXiv:0907.454
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