796 research outputs found
Control networks for the Galilean satellites, November 1979
Pictures of the four Galilean satellites taken as the two Voyager spacecraft approached Jupiter during March and July 1979 are presented. Control nets of the Galilean satellites, computed photogrammetrically, and measurements of the mean radii are presented. The pictures in the control nets are identified, the coordinates of the control points are given, and identifications of some of the control points are shown on figures. The use of star field pictures to compute the focal lengths of the camera is discussed and the geometric relationship between the narrow and wide and angle cameras is reported. A description of the coordinate systems of the Galilean satellites is presented and the status of the control net computations is reported
Screening properties and phase transitions in unconventional plasmas for Ising-type quantum Hall states
Utilizing large-scale Monte-Carlo simulations, we investigate an
unconventional two-component classical plasma in two dimensions which controls
the behavior of the norms and overlaps of the quantum-mechanical wavefunctions
of Ising-type quantum Hall states. The plasma differs fundamentally from that
which is associated with the two-dimensional XY model and Abelian fractional
quantum Hall states. We find that this unconventional plasma undergoes a
Berezinskii-Kosterlitz-Thouless phase transition from an insulator to a metal.
The parameter values corresponding to Ising-type quantum Hall states lie on the
metallic side of this transition. This result verifies the required properties
of the unconventional plasma used to demonstrate that Ising-type quantum Hall
states possess quasiparticles with non-Abelian braiding statistics.Comment: 16 pages, 14 figures. Submitted to Physical Review
Stability of 1-D Excitons in Carbon Nanotubes under High Laser Excitations
Through ultrafast pump-probe spectroscopy with intense pump pulses and a wide
continuum probe, we show that interband exciton peaks in single-walled carbon
nanotubes (SWNTs) are extremely stable under high laser excitations. Estimates
of the initial densities of excitons from the excitation conditions, combined
with recent theoretical calculations of exciton Bohr radii for SWNTs, suggest
that their positions do not change at all even near the Mott density. In
addition, we found that the presence of lowest-subband excitons broadens all
absorption peaks, including those in the second-subband range, which provides a
consistent explanation for the complex spectral dependence of pump-probe
signals reported for SWNTs.Comment: 4 pages, 4 figure
Thermodynamic formalism for the Lorentz gas with open boundaries in dimensions
A Lorentz gas may be defined as a system of fixed dispersing scatterers, with
a single light particle moving among these and making specular collisions on
encounters with the scatterers. For a dilute Lorentz gas with open boundaries
in dimensions we relate the thermodynamic formalism to a random flight
problem. Using this representation we analytically calculate the central
quantity within this formalism, the topological pressure, as a function of
system size and a temperature-like parameter \ba. The topological pressure is
given as the sum of the topological pressure for the closed system and a
diffusion term with a \ba-dependent diffusion coefficient. From the
topological pressure we obtain the Kolmogorov-Sinai entropy on the repeller,
the topological entropy, and the partial information dimension.Comment: 7 pages, 5 figure
Direct Observation of Sub-Poissonian Number Statistics in a Degenerate Bose Gas
We report the direct observation of sub-Poissonian number fluctuation for a
degenerate Bose gas confined in an optical trap. Reduction of number
fluctuations below the Poissonian limit is observed for average numbers that
range from 300 to 60 atoms.Comment: 5 pages, 4 figure
Density expansion for transport coefficients: Long-wavelength versus Fermi surface nonanalyticities
The expansion of the conductivity in 2-d quantum Lorentz models in terms of
the scatterer density n is considered. We show that nonanalyticities in the
density expansion due to scattering processes with small and large momentum
transfers, respectively, have different functional forms. Some of the latter
are not logarithmic, but rather of power-law nature, in sharp contrast to the
3-d case. In a 2-d model with point-like scatterers we find that the leading
nonanalytic correction to the Boltzmann conductivity, apart from the frequency
dependent weak-localization term, is of order n^{3/2}.Comment: 4 pp., REVTeX, epsf, 3 eps figs, final version as publishe
Incorporating interactive 3-dimensional graphics in astronomy research papers
Most research data collections created or used by astronomers are
intrinsically multi-dimensional. In contrast, all visual representations of
data presented within research papers are exclusively 2-dimensional. We present
a resolution of this dichotomy that uses a novel technique for embedding
3-dimensional (3-d) visualisations of astronomy data sets in electronic-format
research papers. Our technique uses the latest Adobe Portable Document Format
extensions together with a new version of the S2PLOT programming library. The
3-d models can be easily rotated and explored by the reader and, in some cases,
modified. We demonstrate example applications of this technique including: 3-d
figures exhibiting subtle structure in redshift catalogues, colour-magnitude
diagrams and halo merger trees; 3-d isosurface and volume renderings of
cosmological simulations; and 3-d models of instructional diagrams and
instrument designs.Comment: 18 pages, 7 figures, submitted to New Astronomy. For paper with
3-dimensional embedded figures, see http://astronomy.swin.edu.au/s2plot/3dpd
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