21,049 research outputs found
Stationary Bianchi type II perfect fluid models
Einstein's field equations for stationary Bianchi type II models with a
perfect fluid source are investigated. The field equations are rewritten as a
system of autonomous first order differential equations. Dimensionless
variables are subsequently introduced for which the reduced phase space is
compact. The system is then studied qualitatively using the theory of dynamical
systems. It is shown that the locally rotationally symmetric models are not
asymptotically self-similar for small values of the independent , tovariable. A
new exact solution is also given.Comment: 6 pages, 1 figure LaTeX. To appear in JM
The micrometeoroid experiment on the OGO 2 satellite
Micrometeoroids in earths dust cloud obtained from OGO-B satellit
Uni-directional polymerization leading to homochirality in the RNA world
The differences between uni-directional and bi-directional polymerization are
considered. The uni-directional case is discussed in the framework of the RNA
world. Similar to earlier models of this type, where polymerization was assumed
to proceed in a bi-directional fashion (presumed to be relevant to peptide
nucleic acids), left-handed and right-handed monomers are produced via an
autocatalysis from an achiral substrate. The details of the bifurcation from a
racemic solution to a homochiral state of either handedness is shown to be
remarkably independent of whether the polymerization in uni-directional or
bi-directional. Slightly larger differences are seen when dissociation is
allowed and the dissociation fragments are being recycled into the achiral
substrate.Comment: 9 pages, 4 figures, submitted to Astrobiolog
Heat capacity mapping mission project HCM-051
There are no author-identified significant results in this report
The Low-level Spectrum of the String
We investigate the spectrum of physical states in the string theory, up
to level 2 for a multi-scalar string, and up to level 4 for the two-scalar
string. The (open) string has a photon as its only massless state. By
using screening charges to study the null physical states in the two-scalar
string, we are able to learn about the gauge symmetries of the states in
the multi-scalar string.Comment: 31 pages, Plain Tex, CTP TAMU-70/92, Goteborg ITP 92-43,
Imperial/TP/91-92/22, KCL-TH-92-
Description of superdeformed bands in light N=Z nuclei using the cranked HFB method
Superdeformed states in light nuclei are studied by means of the
self-consistent cranking calculation (i.e., the P + QQ model based on the
cranked Hartree-Fock-Bogoliubov method). Analyses are given for two typical
cases of superdeformed bands in the mass region, that is, bands
where backbending is absent (Ca) and present (Ar). Investigations
are carried out, particularly for the following points: cross-shell excitations
in the sd and pf shells; the role of the g and d orbitals; the
effect of the nuclear pairing; and the interplay between triaxiality and band
termination.Comment: 17 pages, 18 figures, accepted in Phys. Rev.
The effects of deformation and pairing correlations on nuclear charge form factor
A set of moderately deformed shell nuclei is employed for testing the
reliability of the nuclear ground state wave functions which are obtained in
the context of a BCS approach and offer a simultaneous consideration of
deformation and pairing correlations effects. In this method, the mean field is
assumed to be an axially symmetric Woods-Saxon potential and the effective
two-body interaction is a monopole pairing force. As quantities of main
interest we have chosen the nuclear form factors, the occupancies of the active
(surface) orbits and the Fermi sea depletion, which provide quite good tests
for microscopic descriptions of nuclei within many body theories. For our
comparisons with results emerging from other similar methods, an axially
deformed harmonic oscillator field is also utilized.Comment: 20 pages, 12 figures, 2 table
Heat Capacity Mapping Mission
The Tasman Front was delineated by airborne expendable bathythermograph survey; and an Heat Capacity Mapping Mission (HCMM) IR image on the same day shows the same principal features as determined from ground-truth. It is clear that digital enhancement of HCMM images is necessary to map ocean surface temperatures and when done, the Tasman Front and other oceanographic features can be mapped by this method, even through considerable scattered cloud cover
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