11,835 research outputs found
Chern-Simons Field Theories with Non-semisimple Gauge Group of Symmetry
Subject of this work is a class of Chern-Simons field theories with
non-semisimple gauge group, which may well be considered as the most
straightforward generalization of an Abelian Chern-Simons field theory. As a
matter of fact these theories, which are characterized by a non-semisimple
group of gauge symmetry, have cubic interactions like those of non-abelian
Chern-Simons field theories, but are free from radiative corrections. Moreover,
at the tree level in the perturbative expansion,there are only two connected
tree diagrams, corresponding to the propagator and to the three vertex
originating from the cubic interaction terms. For such theories it is derived
here a set of BRST invariant observables, which lead to metric independent
amplitudes. The vacuum expectation values of these observables can be computed
exactly. From their expressions it is possible to isolate the Gauss linking
number and an invariant of the Milnor type, which describes the topological
relations among three or more closed curves.Comment: 16 pages, 1 figure, plain LaTeX + psfig.st
Lorentz symmetry breaking in the noncommutative Wess-Zumino model: One loop corrections
In this paper we deal with the issue of Lorentz symmetry breaking in quantum
field theories formulated in a non-commutative space-time. We show that, unlike
in some recente analysis of quantum gravity effects, supersymmetry does not
protect the theory from the large Lorentz violating effects arising from the
loop corrections. We take advantage of the non-commutative Wess-Zumino model to
illustrate this point.Comment: 9 pages, revtex4. Corrected references. Version published in PR
Archimedes' law and its corrections for an active particle in a granular sea
We study the origin of buoyancy forces acting on a larger particle moving in
a granular medium subject to horizontal shaking and its corrections before
fluidization. In the fluid limit Archimedes' law is verified; before the limit
memory effects counteract buoyancy, as also found experimentally. The origin of
the friction is an excluded volume effect between active particles, which we
study more exactly for a random walker in a random environment. The same
excluded volume effect is also responsible for the mutual attraction between
bodies moving in the granular medium. Our theoretical modeling proceeds via an
asymmetric exclusion process, i.e., via a dissipative lattice gas dynamics
simulating the position degrees of freedom of a low density granular sea.Comment: 22 pages,5 figure
On the finiteness of the noncommutative supersymmetric Maxwell-Chern-Simons theory
Within the superfield approach, we prove the absence of UV/IR mixing in the
three-dimensional noncommutative supersymmetric Maxwell-Chern-Simons theory at
any loop order and demonstrate its finiteness in one, three and higher loop
orders.Comment: 9 pages, 2 figures, revtex
Bistability of persistent currents in mesoscopic rings
We study the persistent currents flowing in a mesoscopic ring threaded by a
magnetic flux and connected to a stub of finite length. Multistability
processes and Coulomb blockade are demonstrated to be present in this system.
These properties are functions of the magnetic flux crossing the ring which
plays the role that the external applied potential fulfills in the
multistability behaviour of the standard mesoscopic heterostructures.Comment: 13 pages (Revtex), 4 PostScript figures. Send e-mail to:
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The three-dimensional noncommutative Gross-Neveu model
This work is dedicated to the study of the noncommutative Gross-Neveu model.
As it is known, in the canonical Weyl-Moyal approach the model is inconsistent,
basically due to the separation of the amplitudes into planar and nonplanar
parts. We prove that if instead a coherent basis representation is used, the
model becomes renormalizable and free of the aforementioned difficulty. We also
show that, although the coherent states procedure breaks Lorentz symmetry in
odd dimensions, in the Gross-Neveu model this breaking can be kept under
control by assuming the noncommutativity parameters to be small enough. We also
make some remarks on some ordering prescriptions used in the literature.Comment: 10 pages, IOP article style; v3: revised version, accepted for
publication in J. Phys.
Low-Margin Optical-Network Design with Multiple Physical-Layer Parameter Uncertainties
Analytical QoT models require safety margins to account for uncertain knowledge of input parameters. We propose and evaluate a design procedure that gradually decreases these margins in presence of multiple physical-layer uncertainties, by leveraging monitoring data to build a ML-based QoT regressor
Increased sensitivity of DMD lymphoblastoid cell to low doses of X-irradiation.
Several cell membrane abnormalities affecting various cell populations have been reported in Duchenne muscular dystrophy (DMD) by different investigators. In peripheral blood lymphocytes intrinsic cellular membrane defect evidentiated by impairment of capping capacities has been repeatedly obtained, suggesting that DMD product could act in such cellular phenotype at the cytoskeletal compartment. It has been previously reported that lymphoid cells are characterized by high radiosensitivity. On the assumption that DMD phenotypes could increase this susceptibility, we have compared the radiosensitivity of normal and DMD lymphoblastoid cell lines (LCLs) to small doses (0-2Gy) of x-irradiation. The results obtained suggest an increased sensitivity of DMD cells without Ca++ uptake or apoptotic phenomena, associated with an effect upon cell cycle length
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