5,368 research outputs found
The I-mode confinement regime at ASDEX Upgrade: global propert ies and characterization of strongly intermittent density fluctuations
Properties of the IÂmode confinement regime on the ASDEX Upgrade tokamak are
summarized. A weak dependence of the power threshold for the LÂI transition on the toroidal
magnetic field strength is found. During improved confinement, the edge radial electric field
well deepens. Stability calculations show that the IÂmode pedestal is peelingÂballooning stable.
Turbulence investigations reveal strongly intermittent density fluctuations linked to the weakly
coherent mode in the confined plasma, which become stronger as the confinement quality
increases. Across all investigated structure sizes (
â
â„
k
5
â
12 cm
â
1
, with
â„
k
the perpendicular
wavenumber of turbulent density fluctuations), the intermittent turbulence bursts are observed.
Comparison with bolometry data shows that they move poloidally toward the XÂpoint and
finally end up in the divertor. This might be indicative that they play a role in inhibiting the
density profile growth, such that no pedestal is formed in the edge density profile.European Union (EUROfusion 633053)European Union (EUROfusion AWP15ÂENRÂ09/IPPÂ02
Supersymmetric quantum mechanics with nonlocal potentials
We consider supersymmetric quantum mechanical models with both local and
nonlocal potentials. We present a nonlocal deformation of exactly solvable
local models. Its energy eigenfunctions and eigenvalues are determined exactly.
We observe that both our model Hamiltonian and its supersymmetric partner may
have normalizable zero-energy ground states, in contrast to local models with
nonperiodic or periodic potentials.Comment: 4 pages, REVTeX, Minor revisions for clarificatio
Self-DUal SU(3) Chern-Simons Higgs Systems
We explore self-dual Chern-Simons Higgs systems with the local and
global symmetries where the matter field lies in the adjoint
representation. We show that there are three degenerate vacua of different
symmetries and study the unbroken symmetry and particle spectrum in each
vacuum. We classify the self-dual configurations into three types and study
their properties.Comment: Columbia Preprint CU-TP-635, 19 page
Physically meaningful and not so meaningful symmetries in Chern-Simons theory
We explicitly show that the Landau gauge supersymmetry of Chern-Simons theory
does not have any physical significance. In fact, the difference between an
effective action both BRS invariant and Landau supersymmetric and an effective
action only BRS invariant is a finite field redefinition. Having established
this, we use a BRS invariant regulator that defines CS theory as the large mass
limit of topologically massive Yang-Mills theory to discuss the shift k \to
k+\cv of the bare Chern-Simons parameter in conncection with the Landau
supersymmetry. Finally, to convince ourselves that the shift above is not an
accident of our regularization method, we comment on the fact that all BRS
invariant regulators used as yet yield the same value for the shift.Comment: phyzzx, 21 pages, 2 figures in one PS fil
Passage of Time in a Planck Scale Rooted Local Inertial Structure
It is argued that the `problem of time' in quantum gravity necessitates a
refinement of the local inertial structure of the world, demanding a
replacement of the usual Minkowski line element by a 4+2n dimensional
pseudo-Euclidean line element, with the extra 2n being the number of internal
phase space dimensions of the observed system. In the refined structure, the
inverse of the Planck time takes over the role of observer-independent
conversion factor usually played by the speed of light, which now emerges as an
invariant but derivative quantity. In the relativistic theory based on the
refined structure, energies and momenta turn out to be invariantly bounded from
above, and lengths and durations similarly bounded from below, by their
respective Planck scale values. Along the external timelike world-lines, the
theory naturally captures the `flow of time' as a genuinely structural
attribute of the world. The theory also predicts expected
deviations--suppressed quadratically by the Planck energy--from the dispersion
relations for free fields in the vacuum. The deviations from the special
relativistic Doppler shifts predicted by the theory are also suppressed
quadratically by the Planck energy. Nonetheless, in order to estimate the
precision required to distinguish the theory from special relativity, an
experiment with a binary pulsar emitting TeV range gamma-rays is considered in
the context of the predicted deviations from the second-order shifts.Comment: 17 pages; Diagram depicting "the objective flow of time" is replaced
with a much-improved diagra
Implicit Regularization and Renormalization of QCD
We apply the Implicit Regularization Technique (IR) in a non-abelian gauge
theory. We show that IR preserves gauge symmetry as encoded in relations
between the renormalizations constants required by the Slavnov-Taylor
identities at the one loop level of QCD. Moreover, we show that the technique
handles divergencies in massive and massless QFT on equal footing.Comment: (11 pages, 2 figures
Differential Regularization of Topologically Massive Yang-Mills Theory and Chern-Simons Theory
We apply differential renormalization method to the study of
three-dimensional topologically massive Yang-Mills and Chern-Simons theories.
The method is especially suitable for such theories as it avoids the need for
dimensional continuation of three-dimensional antisymmetric tensor and the
Feynman rules for three-dimensional theories in coordinate space are relatively
simple. The calculus involved is still lengthy but not as difficult as other
existing methods of calculation. We compute one-loop propagators and vertices
and derive the one-loop local effective action for topologically massive
Yang-Mills theory. We then consider Chern-Simons field theory as the large mass
limit of topologically massive Yang-Mills theory and show that this leads to
the famous shift in the parameter . Some useful formulas for the calculus of
differential renormalization of three-dimensional field theories are given in
an Appendix.Comment: 25 pages, 4 figures. Several typewritten errors and inappropriate
arguments are corrected, especially the correct adresses of authors are give
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