10,937 research outputs found
The origin of channels and associated deposits in the Elysium region of Mars
Photogeological studies of the Elysium volcanic province of Mars show that its sinuous channels are part of a large deposit which probably was emplaced as a series of huge volcanic debris flows or lahars. The suggestion is based on evidence that the lahars were : (1) gravity-driven mass flow deposits (lobate outlines, steep snouts, smooth medial channels and rough lateral deposits--the deposits narrow and widen in accord with topography, and they extend downslope); (2) wet (channeled surfaces, drainage features); and (3) associated with volcanism (the deposits and channels extend from a system of fractures which fed lava flows). It is conceivable that heat associated with magmatism melted ground ice below the Elysium volcanoes, formed a muddy slurry which issued out of regional fractures and spread over the adjoining plain
Volatile reservoirs below the surface of the Elysium region of Mars: Geomorphic evidence
The Elysium volcanic province contains a variety of geomorphic evidence for the existence of large volatile reservoirs of subsurface volatiles. Study of these landforms yields insight into the distribution and size of these reservoirs and how they interact with the surface environment and will ultimately place constraints on the geometry, constitution, origin, time of formation, and temporal evolution of these important components of the Martian crust. Three principal types of landforms appear to be related to subsurface volatile reservoirs in the Elysium region of Mars: small outflow channels; large lahars; and vast expanses of knobby terranes around the margins of the Elysium dome. The evidence provided by these landforms is internally consistent with the presence of a large relatively shallow volatile reservoir in the Elysium region. If the geologic features described are reliable indicators of subsurface volatiles, they imply that: volatile reservoirs lie relatively close to the surface and underlie millions of sq km in this region; there is no apparent latitudinal variation in the depth or thickness of the volatile reservoirs; the precursors of the knobby terranes are or were important volatile reservoirs; volatiles may be lost in a variety of ways from these reservoirs; and volatiles were incorporated in an easily eroded surficial deposit in the middle history of Mars. The ultimate origin of water in this reservoir is uncertain. A model to explain the preferential entrapment of volatiles into the region's surface materials may be required
Fast algorithms for computing defects and their derivatives in the Regge calculus
Any practical attempt to solve the Regge equations, these being a large
system of non-linear algebraic equations, will almost certainly employ a
Newton-Raphson like scheme. In such cases it is essential that efficient
algorithms be used when computing the defect angles and their derivatives with
respect to the leg-lengths. The purpose of this paper is to present details of
such an algorithm.Comment: 38 pages, 10 figure
Theory of Activated Transport in Bilayer Quantum Hall Systems
We analyze the transport properties of bilayer quantum Hall systems at total
filling factor in drag geometries as a function of interlayer bias, in
the limit where the disorder is sufficiently strong to unbind meron-antimeron
pairs, the charged topological defects of the system. We compute the typical
energy barrier for these objects to cross incompressible regions within the
disordered system using a Hartree-Fock approach, and show how this leads to
multiple activation energies when the system is biased. We then demonstrate
using a bosonic Chern-Simons theory that in drag geometries, current in a
single layer directly leads to forces on only two of the four types of merons,
inducing dissipation only in the drive layer. Dissipation in the drag layer
results from interactions among the merons, resulting in very different
temperature dependences for the drag and drive layers, in qualitative agreement
with experiment.Comment: 4 pages, 2 figure
Probing spacetime foam with extragalactic sources
Due to quantum fluctuations, spacetime is probably ``foamy'' on very small
scales. We propose to detect this texture of spacetime foam by looking for
core-halo structures in the images of distant quasars. We find that the Very
Large Telescope interferometer will be on the verge of being able to probe the
fabric of spacetime when it reaches its design performance. Our method also
allows us to use spacetime foam physics and physics of computation to infer the
existence of dark energy/matter, independent of the evidence from recent
cosmological observations.Comment: LaTeX, 11 pages, 1 figure; version submitted to PRL; several
references added; very useful comments and suggestions by Eric Perlman
incorporate
Self-dual vortices in a Maxwell-Chern-Simons model with non-minimal coupling
We find self-dual vortex solutions in a Maxwell-Chern-Simons model with
anomalous magnetic moment. From a recently developed N=2-supersymmetric
extension, we obtain the proper Bogomol'nyi equations together with a Higgs
potential allowing both topological and non-topological phases in the theory.Comment: 12 pages, 9 figures, 2 tables; some typos corrected, one reference
updated. To be published in the Int. J. Mod. Phys. A (1999
N=2-Maxwell-Chern-Simons model with anomalous magnetic moment coupling via dimensional reduction
An N=1--supersymmetric version of the Cremmer-Scherk-Kalb-Ramond model with
non-minimal coupling to matter is built up both in terms of superfields and in
a component-field formalism. By adopting a dimensional reduction procedure, the
N=2--D=3 counterpart of the model comes out, with two main features: a genuine
(diagonal) Chern-Simons term and an anomalous magnetic moment coupling between
matter and the gauge potential.Comment: 15 pages, Latex; one reference corrected; To be published in the Int.
J. Mod. Phys.
Complex network analysis of literary and scientific texts
We present results from our quantitative study of statistical and network
properties of literary and scientific texts written in two languages: English
and Polish. We show that Polish texts are described by the Zipf law with the
scaling exponent smaller than the one for the English language. We also show
that the scientific texts are typically characterized by the rank-frequency
plots with relatively short range of power-law behavior as compared to the
literary texts. We then transform the texts into their word-adjacency network
representations and find another difference between the languages. For the
majority of the literary texts in both languages, the corresponding networks
revealed the scale-free structure, while this was not always the case for the
scientific texts. However, all the network representations of texts were
hierarchical. We do not observe any qualitative and quantitative difference
between the languages. However, if we look at other network statistics like the
clustering coefficient and the average shortest path length, the English texts
occur to possess more clustered structure than do the Polish ones. This result
was attributed to differences in grammar of both languages, which was also
indicated in the Zipf plots. All the texts, however, show network structure
that differs from any of the Watts-Strogatz, the Barabasi-Albert, and the
Erdos-Renyi architectures
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