329 research outputs found
'Schwinger Model' on the Fuzzy Sphere
In this paper, we construct a model of spinor fields interacting with
specific gauge fields on fuzzy sphere and analyze the chiral symmetry of this
'Schwinger model'. In constructing the theory of gauge fields interacting with
spinors on fuzzy sphere, we take the approach that the Dirac operator on
q-deformed fuzzy sphere is the gauged Dirac operator on fuzzy
sphere. This introduces interaction between spinors and specific one parameter
family of gauge fields. We also show how to express the field strength for this
gauge field in terms of the Dirac operators and alone. Using the path
integral method, we have calculated the point functions of this model and
show that, in general, they do not vanish, reflecting the chiral non-invariance
of the partition function.Comment: Minor changes, typos corrected, 18 pages, to appear in Mod. Phys.
Lett.
Electrodynamics on -Minkowski space-time
In this paper, we derive Lorentz force and Maxwell's equations on
kappa-Minkowski space-time up to the first order in the deformation parameter.
This is done by elevating the principle of minimal coupling to non-commutative
space-time. We also show the equivalence of minimal coupling prescription and
Feynman's approach. It is shown that the motion in kappa space-time can be
interpreted as motion in a background gravitational field, which is induced by
this non-commutativity. In the static limit, the effect of kappa deformation is
to scale the electric charge. We also show that the laws of electrodynamics
depend on the mass of the charged particle, in kappa space-time.Comment: 16 pages,minor changes, paragraph added on page 13, two new
references added, to appear in Phys.Rev.
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
Assessment of Heavy Metal Contamination in the Sediments of a River Draining into a Ramsar Site in the Indian Subcontinent
Concentrations of six heavy metals (Cd, Cr, Ni, Zn, Pb and Cu) in surface sediments of Achankovil river basin which is draining into a Ramsar site in India viz. The Vembanad wetland system was determined. To assess metal concentrations in sediment, numeric Sediment Quality Guidelines (SQGs) were employed. The concentrations of Zn, Cr and Pb in all sediment samples are lower than the proposed threshold effect concentrations which indicate that there are no harmful effects from these metals. On the other hand, the concentrations of Cd in one station, Cu in three stations and Ni in all stations exceeded the threshold effect concentrations indicated that these stations were in potential risk. The metal contamination in sediments was evaluated by applying Index geoaccumulation, metal pollution index, Enrichment factor and Multivariate statistical techniques. The low values of EF show that the enrichment of sediment by heavy metal was by natural processes
Intelligent Buffer Management Algorithm to Prevent Packet loss in Mobile Adhoc Network
In a mobile ad hoc network, which is self-organized and operates without any fundamental infrastructure, packet transmission from the source node to the destination node is completed after sending the route request and route reply. A reliable path is then selected depending on the protocol choice. Data that the sender intends to deliver is broken up into packets and given sequence numbers before being transmitted over the channel. With the aid of an internal buffer that helps to receive packets and forward them to the next destination, each and every packet travels along the allotted path until it reaches its destination. If there is more traffic on the MANET, the buffer may overflow, which will result in packet loss during transmission.. The source node must retransmit to the destination if any packets were lost during the initial transfer. This article proposes the Intelligent Buffer Management (IBM) active buffer management algorithm to prevent such a scenario by enhancing the MANET nodes' buffers to prevent packet loss. The Network Simulator is used to help build this suggested approach, and the results are compared to those of the current buffer management method to show that IBM is superior
Challenges on Missing Packet Detection or Packet Dropping Attacks in Mobile Adhoc Network -A Survey
Collection of wireless nodes forms together to communicate each other in the network without infrastructure less and any access point along with the characteristics of freedom in mobility is called Mobile Adhoc Network. Transmitting of packets from source to destination plays the vital role in MANET. When a Packet is not delivered properly at the destination , its affects the performance of the MANET. Due to this characteristics of the mobility nodes can subject to falls on the packet missing also the various packets dropping security attacks take part in the dropping the packets while communication to achieve the decreasing the performance of the MANET. This article focus on the survey about the missing packet assembly as well the packet dropping security attacks in MANET
Abelian 2-form gauge theory: special features
It is shown that the four -dimensional (4D) free Abelian 2-form
gauge theory provides an example of (i) a class of field theoretical models for
the Hodge theory, and (ii) a possible candidate for the quasi-topological field
theory (q-TFT). Despite many striking similarities with some of the key
topological features of the two -dimensional (2D) free Abelian (and
self-interacting non-Abelian) gauge theories, it turns out that the 4D free
Abelian 2-form gauge theory is {\it not} an exact TFT. To corroborate this
conclusion, some of the key issues are discussed. In particular, it is shown
that the (anti-)BRST and (anti-)co-BRST invariant quantities of the 4D 2-form
Abelian gauge theory obey the recursion relations that are reminiscent of the
exact TFTs but the Lagrangian density of this theory is not found to be able to
be expressed as the sum of (anti-)BRST and (anti-)co-BRST exact quantities as
is the case with the {\it topological} 2D free Abelian (and self-interacting
non-Abelian) gauge theories.Comment: LaTeX, 23 pages, journal ref. give
Gauge Transformations, BRST Cohomology and Wigner's Little Group
We discuss the (dual-)gauge transformations and BRST cohomology for the two
(1 + 1)-dimensional (2D) free Abelian one-form and four (3 + 1)-dimensional
(4D) free Abelian 2-form gauge theories by exploiting the (co-)BRST symmetries
(and their corresponding generators) for the Lagrangian densities of these
theories. For the 4D free 2-form gauge theory, we show that the changes on the
antisymmetric polarization tensor e^{\mu\nu} (k) due to (i) the (dual-)gauge
transformations corresponding to the internal symmetry group, and (ii) the
translation subgroup T(2) of the Wigner's little group, are connected with
each-other for the specific relationships among the parameters of these
transformation groups. In the language of BRST cohomology defined w.r.t. the
conserved and nilpotent (co-)BRST charges, the (dual-)gauge transformed states
turn out to be the sum of the original state and the (co-)BRST exact states. We
comment on (i) the quasi-topological nature of the 4D free 2-form gauge theory
from the degrees of freedom count on e^{\mu\nu} (k), and (ii) the Wigner's
little group and the BRST cohomology for the 2D one-form gauge theory {\it
vis-{\`a}-vis} our analysis for the 4D 2-form gauge theory.Comment: LaTeX file, 29 pages, misprints in (3.7), (3.8), (3.9), (3.13) and
(4.14)corrected and communicated to IJMPA as ``Erratum'
The Central Charge of the Warped AdS^3 Black Hole
The AdS/CFT conjecture offers the possibility of a quantum description for a
black hole in terms of a CFT. This has led to the study of general AdS^3 type
black holes with a view to constructing an explicit toy quantum black hole
model. Such a CFT description would be characterized by its central charge and
the dimensions of its primary fields. Recently the expression for the central
charges (C_L, C_R) of the CFT dual to the warped AdS^3 have been determined
using asymptotic symmetry arguments. The central charges depend, as expected,
on the warping factor. We show that topological arguments, used by Witten to
constrain central charges for the BTZ black hole, can be generalized to deal
with the warped AdS^3 case. Topology constrains the warped factor to be
rational numbers while quasinormal modes are conjectured to give the dimensions
of primary fields. We find that in the limit when warping is large or when it
takes special rational values the system tends to Witten's conjectured unique
CFT's with central charges that are multiples of 24.Comment: 6 pages, Latex fil
BRST analysis of topologically massive gauge theory: novel observations
A dynamical non-Abelian 2-form gauge theory (with B \wedge F term) is endowed
with the "scalar" and "vector" gauge symmetry transformations. In our present
endeavor, we exploit the latter gauge symmetry transformations and perform the
Becchi-Rouet-Stora-Tyutin (BRST) analysis of the four (3 + 1)-dimensional (4D)
topologically massive non-Abelian 2-form gauge theory. We demonstrate the
existence of some novel features that have, hitherto, not been observed in the
context of BRST approach to 4D (non-)Abelian 1-form as well as Abelian 2-form
and 3-form gauge theories. We comment on the differences between the novel
features that emerge in the BRST analysis of the "scalar" and "vector" gauge
symmetries of the theory.Comment: LaTeX file, 14 pages, an appendix added, references expanded, version
to appear in EPJ
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