29,251 research outputs found
Chaotic string-capture by black hole
We consider a macroscopic charge-current carrying (cosmic) string in the
background of a Schwarzschild black hole. The string is taken to be circular
and is allowed to oscillate and to propagate in the direction perpendicular to
its plane (that is parallel to the equatorial plane of the black hole).
Nurmerical investigations indicate that the system is non-integrable, but the
interaction with the gravitational field of the black hole anyway gives rise to
various qualitatively simple processes like "adiabatic capture" and "string
transmutation".Comment: 13 pages Latex + 3 figures (not included), Nordita 93/55
Fields in Nonaffine Bundles. I. The general bitensorially covariant differentiation procedure
The standard covariant differentiation procedure for fields in vector bundles
is generalised so as to be applicable to fields in general nonaffine bundles in
which the fibres may have an arbitrary nonlinear structure. In addition to the
usual requirement that the base space should be flat or endowed with its own
linear connection, and that there should be an ordinary gauge connection on the
bundle, it is necessary to require also that there should be an intrinsic,
bundle-group invariant connection on the fibre space. The procedure is based on
the use of an appropriate primary-field (i.e. section) independent connector
that is constructed in terms of the natural fibre-tangent-vector realisation of
the gauge connection. The application to gauged harmonic mappings will be
described in a following article.Comment: 17 page Latex file with some minor misprint corrections and added
color for article originally published in black and whit
Poly-essential and general Hyperelastic World (brane) models
This article provides a unified treatment of an extensive category of
non-linear classical field models whereby the universe is represented (perhaps
as a brane in a higher dimensional background) in terms of a structure of a
mathematically convenient type describable as hyperelastic, for which a
complete set of equations of motion is provided just by the energy-momentum
conservation law. Particular cases include those of a perfect fluid in
quintessential backgrounds of various kinds, as well as models of the elastic
solid kind that has been proposed to account for cosmic acceleration. It is
shown how an appropriately generalised Hadamard operator can be used to
construct a symplectic structure that controles the evolution of small
perturbations, and that provides a characteristic equation governing the
propagation of weak discontinuities of diverse (extrinsic and extrinsic) kinds.
The special case of a poly-essential model - the k-essential analogue of an
ordinary polytropic fluid - is examined and shown to be well behaved (like the
fluid) only if the pressure to density ratio is positive.Comment: 16 pages Latex, Contrib. to 10th Peyresq Pysics Meeting, June 2005:
Micro and Macro Structures of Spacetim
Symplectic structure for elastic and chiral conducting cosmic string models
This article is based on the covariant canonical formalism and corresponding
symplectic structure on phase space developed by Witten, Zuckerman and others
in the context of field theory. After recalling the basic principles of this
procedure, we construct the conserved bilinear symplectic current for generic
elastic string models. These models describe current carrying cosmic strings
evolving in an arbitrary curved background spacetime. Particular attention is
paid to the special case of the chiral string for which the worldsheet current
is null. Different formulations of the chiral string action are discussed in
detail, and as a result the integrability property of the chiral string is
clarified.Comment: 18 page
Apparatus for mixing solutions in low gravity environments
An apparatus is disclosed for allowing mixing of solutions in low gravity environments so as to carry out crystallization of proteins and other small molecules or other chemical syntheses, under conditions that maximize crystal growth and minimize disruptive turbulent effects. The apparatus is comprised of a housing, a plurality of chambers, and a cylindrical rotatable valve disposed between at least two of the chambers, said valve having an internal passageway so as to allow fluid movement between the chambers by rotation of the valve. In an alternate embodiment of the invention, a valve is provided having an additional internal passage way so that fluid from a third chamber can be mixed with the fluids of the first two chambers. This alternate embodiment of the invention is particularly desirable when it is necessary to provide a termination step to the crystal growth, or if a second synthetic step is required
Quantum integrability of quadratic Killing tensors
Quantum integrability of classical integrable systems given by quadratic
Killing tensors on curved configuration spaces is investigated. It is proven
that, using a "minimal" quantization scheme, quantum integrability is insured
for a large class of classic examples.Comment: LaTeX 2e, no figure, 35 p., references added, minor modifications. To
appear in the J. Math. Phy
Dynamics of cosmic strings and springs; a covariant formulation
A general family of charge-current carrying cosmic string models is
investigated. In the special case of circular configurations in arbitrary
axially symmetric gravitational and electromagnetic backgrounds the dynamics is
determined by simple point particle Hamiltonians. A certain "duality"
transformation relates our results to previous ones, obtained by Carter et.
al., for an infinitely long open stationary string in an arbitrary stationary
background.Comment: 11 pages, Latex, Nordita preprint 93/28
Resident Impacts of Immigration: Perspectives from America’s Age of Mass Migration
Elementary economic models are often used to suggest that immigration depresses the wages of native-born workers. These models assume that when immigrants enter a labour market, all other features of that market remain unchanged. Such an assumption is almost never valid. Here we explore the economic impacts of immigrants during America’s Age of Mass Migration a century ago. This was a period of dynamic structural change that witnessed the appearance of new industries, adoption of new technologies, discovery of new mineral resources, the rise of big business, and the geographic concentration of industries. We show that immigrants – and residents – selected destinations where labour demand and wages were rising. Thus, native workers experienced wage increases in the presence of heavy immigration. Models that abstract from the special characteristics of labour markets that attract immigrants misrepresent their economic impact.Immigration, Internal migration, Economic history of immigration, Counterfactual analysis
Introductory workshops on remote sensing as related to geological problems in Georgia
There are no author-identified significant results in this report
- …