456 research outputs found
The Pioneer Anomaly and a Machian Universe
We discuss astronomical and astrophysical evidence, which we relate to the
principle of zero-total energy of the Universe, that imply several relations
among the mass M, the radius R and the angular momentum L of a "large" sphere
representing a Machian Universe. By calculating the angular speed, we find a
peculiar centripetal acceleration for the Universe. This is an ubiquituous
property that relates one observer to any observable. It turns out that this is
exactly the anomalous acceleration observed on the Pioneers spaceships. We have
thus, shown that this anomaly is to be considered a property of the Machian
Universe. We discuss several possible arguments against our proposal.Comment: 6 pages including front page. Publishe
Global embeddings of scalar-tensor theories in (2+1)-dimensions
We obtain (3+3)- or (3+2)-dimensional global flat embeddings of four
uncharged and charged scalar-tensor theories with the parameters B or L in the
(2+1)-dimensions, which are the non-trivially modified versions of the
Banados-Teitelboim-Zanelli (BTZ) black holes. The limiting cases B=0 or L=0
exactly are reduced to the Global Embedding Minkowski Space (GEMS) solution of
the BTZ black holes.Comment: 19 pages, 2 figure
Palaeoproterozoic magnesite: lithological and isotopic evidence for playa/sabkha environments
Magnesite forms a series of 1- to 15-m-thick beds within the approximate to2.0 Ga (Palaeoproterozoic) Tulomozerskaya Formation, NW Fennoscandian Shield, Russia. Drillcore material together with natural exposures reveal that the 680-m-thick formation is composed of a stromatolite-dolomite-'red bed' sequence formed in a complex combination of shallow-marine and non-marine, evaporitic environments. Dolomite-collapse breccia, stromatolitic and micritic dolostones and sparry allochemical dolostones are the principal rocks hosting the magnesite beds. All dolomite lithologies are marked by delta C-13 values from +7.1 parts per thousand to +11.6 parts per thousand (V-PDB) and delta O-18 ranging from 17.4 parts per thousand to 26.3 parts per thousand (V-SMOW). Magnesite occurs in different forms: finely laminated micritic; stromatolitic magnesite; and structureless micritic, crystalline and coarsely crystalline magnesite. All varieties exhibit anomalously high delta C-13 values ranging from +9.0 parts per thousand to +11.6 parts per thousand and delta O-18 values of 20.0-25.7 parts per thousand. Laminated and structureless micritic magnesite forms as a secondary phase replacing dolomite during early diagenesis, and replaced dolomite before the major phase of burial. Crystalline and coarsely crystalline magnesite replacing micritic magnesite formed late in the diagenetic/metamorphic history. Magnesite apparently precipitated from sea water-derived brine, diluted by meteoric fluids. Magnesitization was accomplished under evaporitic conditions (sabkha to playa lake environment) proposed to be similar to the Coorong or Lake Walyungup coastal playa magnesite. Magnesite and host dolostones formed in evaporative and partly restricted environments; consequently, extremely high delta C-13 values reflect a combined contribution from both global and local carbon reservoirs. A C- 13-rich global carbon reservoir (delta C-13 at around +5 parts per thousand) is related to the perturbation of the carbon cycle at 2.0 Ga, whereas the local enhancement in C-13 (up to +12 parts per thousand) is associated with evaporative and restricted environments with high bioproductivity
Discrete Symmetries and Generalized Fields of Dyons
We have studied the different symmetric properties of the generalized
Maxwell's - Dirac equation along with their quantum properties. Applying the
parity (\mathcal{P}), time reversal (\mathcal{T}), charge conjugation
(\mathcal{C}) and their combined effect like parity time reversal
(\mathcal{PT}), charge conjugation and parity (\mathcal{CP}) and \mathcal{CP}T
transformations to varius equations of generalized fields of dyons, it is shown
that the corresponding dynamical quantities and equations of dyons are
invariant under these discrete symmetries.
Abstract Key words- parity, time reversal, charge-conjugation, dyons
Abstract PACS No.- 14.80 Hv
Energy Distribution associated with Static Axisymmetric Solutions
This paper has been addressed to a very old but burning problem of energy in
General Relativity. We evaluate energy and momentum densities for the static
and axisymmetric solutions. This specializes to two metrics, i.e., Erez-Rosen
and the gamma metrics, belonging to the Weyl class. We apply four well-known
prescriptions of Einstein, Landau-Lifshitz, Papaterou and Mller to
compute energy-momentum density components. We obtain that these prescriptions
do not provide similar energy density, however momentum becomes constant in
each case. The results can be matched under particular boundary conditions.Comment: 18 pages, accepted for publication in Astrophysics and SpaceScienc
Quantum mechanics: Myths and facts
A common understanding of quantum mechanics (QM) among students and practical
users is often plagued by a number of "myths", that is, widely accepted claims
on which there is not really a general consensus among experts in foundations
of QM. These myths include wave-particle duality, time-energy uncertainty
relation, fundamental randomness, the absence of measurement-independent
reality, locality of QM, nonlocality of QM, the existence of well-defined
relativistic QM, the claims that quantum field theory (QFT) solves the problems
of relativistic QM or that QFT is a theory of particles, as well as myths on
black-hole entropy. The fact is that the existence of various theoretical and
interpretational ambiguities underlying these myths does not yet allow us to
accept them as proven facts. I review the main arguments and counterarguments
lying behind these myths and conclude that QM is still a
not-yet-completely-understood theory open to further fundamental research.Comment: 51 pages, pedagogic review, revised, new references, to appear in
Found. Phy
Discontinuity Induced Bifurcations in a Model of Saccharomyces cerevisiae
We perform a bifurcation analysis of the mathematical model of Jones and
Kompala [K.D. Jones and D.S. Kompala, Cybernetic model of the growth dynamics
of Saccharomyces cerevisiae in batch and continuous cultures, J. Biotech.,
71:105-131, 1999]. Stable oscillations arise via Andronov-Hopf bifurcations and
exist for intermediate values of the dilution rate as has been noted from
experiments previously. A variety of discontinuity induced bifurcations arise
from a lack of global differentiability. We identify and classify discontinuous
bifurcations including several codimension-two scenarios. Bifurcation diagrams
are explained by a general unfolding of these singularities.Comment: 23 pages, 7 figure
Aspects of Bifurcation Theory for Piecewise-Smooth, Continuous Systems
Systems that are not smooth can undergo bifurcations that are forbidden in
smooth systems. We review some of the phenomena that can occur for
piecewise-smooth, continuous maps and flows when a fixed point or an
equilibrium collides with a surface on which the system is not smooth. Much of
our understanding of these cases relies on a reduction to piecewise linearity
near the border-collision. We also review a number of codimension-two
bifurcations in which nonlinearity is important.Comment: pdfLaTeX, 9 figure
Teleparallel Version of the Levi-Civita Vacuum Solutions and their Energy Contents
In this paper, we find the teleparallel version of the Levi-Civita metric and
obtain tetrad and the torsion fields. The tensor, vector and the axial-vector
parts of the torsion tensor are evaluated. It is found that the vector part
lies along the radial direction only while the axial-vector vanishes everywhere
because the metric is diagonal. Further, we use the teleparallel version of
Mller, Einstein, Landau-Lifshitz and Bergmann-Thomson prescriptions
to find the energy-momentum distribution of this metric and compare the results
with those already found in General Relativity. It is worth mentioning here
that momentum is constant in both the theories for all the prescriptions. The
energy in teleparallel theory is equal to the corresponding energy in GR only
in Mller prescription for the remaining prescriptions, the energy do
not agree in both theories. We also conclude that Mller's
energy-momentum distribution is independent of the coupling constant
in the teleparallel theory.Comment: 15 pages, accepted for publication in Canadian J. Physic
Ignition conditions for inertial confinement fusion targets with a nuclear spin-polarized DT fuel
The nuclear fusion cross-section is modified when the spins of the interacting nuclei are polarized. In the case of deuterium?tritium it has been theoretically predicted that the nuclear fusion cross-section could be increased by a factor d = 1.5 if all the nuclei were polarized. In inertial confinement fusion this would result in a modification of the required ignition conditions. Using numerical simulations it is found that the required hot-spot temperature and areal density can both be reduced by about 15% for a fully polarized nuclear fuel. Moreover, numerical simulations of a directly driven capsule show that the required laser power and energy to achieve a high gain scale as d-0.6 and d-0.4 respectively, while the maximum achievable energy gain scales as d0.9
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