995 research outputs found
On the Axiomatics of the 5-dimensional Projective Unified Field Theory of Schmutzer
For more than 40 years E.Schmutzer has developed a new approach to the
(5-dimensional) projective relativistic theory which he later called Projective
Unified Field Theory (PUFT). In the present paper we introduce a new axiomatics
for Schmutzer's theory. By means of this axiomatics we can give a new
geometrical interpretation of the physical concept of the PUFT.Comment: 32 pages, 1 figure, LaTeX 2e, will be submitted to Genaral Relativity
and Gravitatio
Early evolution of electron cyclotron driven current during suppression of tearing modes in a circular tokamak
When electron cyclotron (EC) driven current is first applied to the inside of
a magnetic island, the current spreads throughout the island and after a short
period achieves a steady level. Using a two equation fluid model for the EC
current that allows us to examine this early evolution in detail, we analyze
high-resolution simulations of a 2/1 classical tearing mode in a low-beta large
aspect-ratio circular tokamak. These simulations use a nonlinear 3D reduced-MHD
fluid model and the JOREK code. During the initial period where the EC driven
current grows and spreads throughout the magnetic island, it is not a function
of the magnetic flux. However, once it has reached a steady-state, it should be
a flux function. We demonstrate numerically that if sufficiently resolved
toroidally, the steady-state EC driven current becomes approximately a flux
function. We discuss the physics of this early period of EC evolution and its
impact on the size of the magnetic island.Comment: 12 pages, 7 figure
Null Geodesics in Five Dimensional Manifolds
We analyze a class of 5D non-compact warped-product spaces characterized by
metrics that depend on the extra coordinate via a conformal factor. Our model
is closely related to the so-called canonical coordinate gauge of Mashhoon et
al. We confirm that if the 5D manifold in our model is Ricci-flat, then there
is an induced cosmological constant in the 4D sub-manifold. We derive the
general form of the 5D Killing vectors and relate them to the 4D Killing
vectors of the embedded spacetime. We then study the 5D null geodesic paths and
show that the 4D part of the motion can be timelike -- that is, massless
particles in 5D can be massive in 4D. We find that if the null trajectories are
affinely parameterized in 5D, then the particle is subject to an anomalous
acceleration or fifth force. However, this force may be removed by
reparameterization, which brings the correct definition of the proper time into
question. Physical properties of the geodesics -- such as rest mass variations
induced by a variable cosmological ``constant'', constants of the motion and 5D
time-dilation effects -- are discussed and are shown to be open to experimental
or observational investigation.Comment: 19 pages, REVTeX, in press in Gen. Rel. Gra
The Structure of the Big Bang from Higher-Dimensional Embeddings
We give relations for the embedding of spatially-flat
Friedmann-Robertson-Walker cosmological models of Einstein's theory in flat
manifolds of the type used in Kaluza-Klein theory. We present embedding
diagrams that depict different 4D universes as hypersurfaces in a higher
dimensional flat manifold. The morphology of the hypersurfaces is found to
depend on the equation of state of the matter. The hypersurfaces possess a
line-like curvature singularity infinitesimally close to the
3-surface, where is the time expired since the big bang. The family of
timelike comoving geodesics on any given hypersurface is found to have a
caustic on the singular line, which we conclude is the 5D position of the
point-like big bang.Comment: 11 pages, 5 figures, revtex4, accepted in Class. Quant. Gra
A Class of Anisotropic Five-Dimensional Solutions for the Early Universe
We solve the Ricci-flat equations of extended general relativity to obtain an
interesting class of cosmological models. The solutions are analogous to the 4D
ones of Bianchi type-I of Kasner type and have significant implications for
astrophysics.Comment: V2 has some minor editorial changes in the introductio
Submanifolds in five-dimensional pseudo-Euclidean spaces and four-dimensional FRW universes
Equations for submanifolds, which correspond to embeddings of the
four-dimensional FRW universes in five-dimensional pseudo-Euclidean spaces, are
presented in convenient form in general case. Several specific examples are
considered.Comment: 7 pages, LaTeX, the mathematical part of this paper is based on the
withdrawn preprint arXiv:1012.0320 [gr-qc
On the embedding of branes in five-dimensional spaces
We investigate the embedding of four-dimensional branes in five-dimensional
spaces. We firstly consider the case when the embedding space is a vacuum bulk
whose energy-momentum tensor consists of a Dirac delta function with support in
the brane. We then consider the embedding in the context of
Randall-Sundrum-type models, taking into account symmetry and a
cosmological constant. We employ the Campbell-Magaard theorem to construct the
embeddings and are led to the conclusion that the content of energy-matter of
the brane does not necessarily determine its curvature. Finally, as an
application to illustrate our results, we construct the embedding of Minkowski
spacetime filled with dust.Comment: 12 pages - REVTEX To appear in Classical and Quantum Gravit
Gyrofluid simulations of collisionless reconnection in the presence of diamagnetic effects
The effects of the ion Larmor radius on magnetic reconnection are
investigated by means of numerical simulations, with a Hamiltonian gyrofluid
model. In the linear regime, it is found that ion diamagnetic effects decrease
the growth rate of the dominant mode. Increasing ion temperature tends to make
the magnetic islands propagate in the ion diamagnetic drift direction. In the
nonlinear regime, diamagnetic effects reduce the final width of the island.
Unlike the electron density, the guiding center density does not tend to
distribute along separatrices and at high ion temperature, the electrostatic
potential exhibits the superposition of a small scale structure, related to the
electron density, and a large scale structure, related to the ion
guiding-center density
Gyrofluid simulations of collisionless reconnection in the presence of diamagnetic effects
The effects of the ion Larmor radius on magnetic reconnection are
investigated by means of numerical simulations, with a Hamiltonian gyrofluid
model. In the linear regime, it is found that ion diamagnetic effects decrease
the growth rate of the dominant mode. Increasing ion temperature tends to make
the magnetic islands propagate in the ion diamagnetic drift direction. In the
nonlinear regime, diamagnetic effects reduce the final width of the island.
Unlike the electron density, the guiding center density does not tend to
distribute along separatrices and at high ion temperature, the electrostatic
potential exhibits the superposition of a small scale structure, related to the
electron density, and a large scale structure, related to the ion
guiding-center density
Gyrofluid simulations of collisionless reconnection in the presence of diamagnetic effects
The effects of the ion Larmor radius on magnetic reconnection are
investigated by means of numerical simulations, with a Hamiltonian gyrofluid
model. In the linear regime, it is found that ion diamagnetic effects decrease
the growth rate of the dominant mode. Increasing ion temperature tends to make
the magnetic islands propagate in the ion diamagnetic drift direction. In the
nonlinear regime, diamagnetic effects reduce the final width of the island.
Unlike the electron density, the guiding center density does not tend to
distribute along separatrices and at high ion temperature, the electrostatic
potential exhibits the superposition of a small scale structure, related to the
electron density, and a large scale structure, related to the ion
guiding-center density
- …