99,019 research outputs found
Noncommutativity and Duality through the Symplectic Embedding Formalism
This work is devoted to review the gauge embedding of either commutative and
noncommutative (NC) theories using the symplectic formalism framework. To sum
up the main features of the method, during the process of embedding, the
infinitesimal gauge generators of the gauge embedded theory are easily and
directly chosen. Among other advantages, this enables a greater control over
the final Lagrangian and brings some light on the so-called "arbitrariness
problem". This alternative embedding formalism also presents a way to obtain a
set of dynamically dual equivalent embedded Lagrangian densities which is
obtained after a finite number of steps in the iterative symplectic process,
oppositely to the result proposed using the BFFT formalism. On the other hand,
we will see precisely that the symplectic embedding formalism can be seen as an
alternative and an efficient procedure to the standard introduction of the
Moyal product in order to produce in a natural way a NC theory. In order to
construct a pedagogical explanation of the method to the nonspecialist we
exemplify the formalism showing that the massive NC U(1) theory is embedded in
a gauge theory using this alternative systematic path based on the symplectic
framework. Further, as other applications of the method, we describe exactly
how to obtain a Lagrangian description for the NC version of some systems
reproducing well known theories. Naming some of them, we use the procedure in
the Proca model, the irrotational fluid model and the noncommutative self-dual
model in order to obtain dual equivalent actions for these theories. To
illustrate the process of noncommutativity introduction we use the chiral
oscillator and the nondegenerate mechanics
Studies of the nucler equation of state using numerical calculations of nuclear drop collisions
A numerical calculation for the full thermal dynamics of colliding nuclei was developed. Preliminary results are reported for the thermal fluid dynamics in such processes as Coulomb scattering, fusion, fusion-fission, bulk oscillations, compression with heating, and collisions of heated nuclei
The Influence of Nuclear Composition on the Electron Fraction in the Post-Core-Bounce Supernova Environment
We study the early evolution of the electron fraction (or, alternatively, the
neutron-to-proton ratio) in the region above the hot proto-neutron star formed
after a supernova explosion. We study the way in which the electron fraction in
this environment is set by a competition between lepton (electron, positron,
neutrino, and antineutrino) capture processes on free neutrons and protons and
nuclei. Our calculations take explicit account of the effect of nuclear
composition changes, such as formation of alpha particles (the alpha effect)
and the shifting of nuclear abundances in nuclear statistical equilibrium
associated with cooling in near-adiabatic outflow. We take detailed account of
the process of weak interaction freeze-out in conjunction with these nuclear
composition changes. Our detailed treatment shows that the alpha effect can
cause significant increases in the electron fraction, while neutrino and
antineutrino capture on heavy nuclei tends to have a buffering effect on this
quantity. We also examine the effect on weak rates and the electron fraction of
fluctuations in time in the neutrino and antineutrino energy spectra arising
from hydrodynamic waves. Our analysis is guided by the Mayle & Wilson supernova
code numerical results for the neutrino energy spectra and density and velocity
profiles.Comment: 38 pages, AAS LaTeX, 8 figure
Structure of Micro-instabilities in Tokamak Plasmas: Stiff Transport or Plasma Eruptions?
Solutions to a model 2D eigenmode equation describing micro-instabilities in
tokamak plasmas are presented that demonstrate a sensitivity of the mode
structure and stability to plasma profiles. In narrow regions of parameter
space, with special plasma profiles, a maximally unstable mode is found that
balloons on the outboard side of the tokamak. This corresponds to the
conventional picture of a ballooning mode. However, for most profiles this mode
cannot exist and instead a more stable mode is found that balloons closer to
the top or bottom of the plasma. Good quantitative agreement with a 1D
ballooning analysis is found provided the constraints associated with higher
order profile effects, often neglected, are taken into account. A sudden
transition from this general mode to the more unstable ballooning mode can
occur for a critical flow shear, providing a candidate model for why some
experiments observe small plasma eruptions (Edge Localised Modes, or ELMs) in
place of large Type I ELMs.Comment: 11 pages, 3 figure
The effect of equine hyperimmune sera on TNF alpha activity in a L929 cell bioassay
In this pilot study we examined the effect of sera from a proprietary hyperimmune plasma product (Equiplas) on the activity of TNF: in an in vitro L929 cell bioassay. In brief, we report observations from 2 accessions of sera. Accession 1 describes the antiTNF: activity of 3 hyperimmune sera and an untreated serum sample that were provided blind to the study. Accession 2 reports a comparison of antiTNFalpha activity found in 3 paired hyperimmune sera collected following a multiple endotoxin vaccination regimen
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