424 research outputs found
Geomorphic analyses from space imagery
One of the most obvious applications of space imagery to geomorphological analyses is in the study of drainage patterns and channel networks. LANDSAT, high altitude photography and other types of remote sensing imagery are excellent for depicting stream networks on a regional scale because of their broad coverage in a single image. They offer a valuable tool for comparing and analyzing drainage patterns and channel networks all over the world. Three aspects considered in this geomorphological study are: (1) the origin, evolution and rates of development of drainage systems; (2) the topological studies of network and channel arrangements; and (3) the adjustment of streams to tectonic events and geologic structure (i.e., the mode and rate of adjustment)
Photodetachment of cold OH- in a multipole ion trap
The absolute photodetachment cross section of OH- anions at a rotational and
translational temperature of 170K is determined by measuring the
detachment-induced decay rate of the anions in a multipole radio-frequency ion
trap. In comparison with previous results, the obtained cross section shows the
importance of the initial rotational state distribution. Using a tomography
scan of the photodetachment laser through the trapped ion cloud, the derived
cross section is model-independent and thus features a small systematic
uncertainty. The tomography also yields the column density of the OH- anions in
the 22-pole ion trap in good agreement with the expected trapping potential of
a large field free region bound by steep potential walls.Comment: Phys. Rev. Lett., in pres
Vacuum solutions of five dimensional Einstein equations generated by inverse scattering method
We study stationary and axially symmetric two solitonic solutions of five
dimensional vacuum Einstein equations by using the inverse scattering method
developed by Belinski and Zakharov. In this generation of the solutions, we use
five dimensional Minkowski spacetime as a seed. It is shown that if we restrict
ourselves to the case of one angular momentum component, the generated solution
coincides with a black ring solution with a rotating two sphere which was found
by Mishima and Iguchi recently.Comment: 10 pages, accepted for publication in Physical Review
Boundary Value Problem for Black Rings
We study the boundary value problem for asymptotically flat stationary black
ring solutions to the five-dimensional vacuum Einstein equations. Assuming the
existence of two additional commuting axial Killing vector fields and the
horizon topology of , we show that the only asymptotically flat
black ring solution with a regular horizon is the Pomeransky-Sen'kov black ring
solution.Comment: 21 pages, 1 figur
Energy flux through the horizon in the black hole-domain wall systems
We study various configurations in which a domain wall (or cosmic string),
described by the Nambu-Goto action, is embedded in a background space-time of a
black hole in and higher dimensional models. We calculate energy fluxes
through the black hole horizon. In the simplest case, when a static domain wall
enters the horizon of a static black hole perperdicularly, the energy flux is
zero. In more complicated situations, where parameters which describe the
domain wall surface are time and position dependent, the flux is non-vanishing
is principle. These results are of importance in various conventional
cosmological models which accommodate the existence of domain walls and strings
and also in brane world scenarios.Comment: references added, accepted for publication in JHE
Thick domain walls around a black hole
We discuss the gravitationally interacting system of a thick domain wall and
a black hole. We numerically solve the scalar field equation in the
Schwarzschild spacetime and obtain a sequence of static axi-symmetric solutions
representing thick domain walls. We find that, for the walls near the horizon,
the Nambu--Goto approximation is no longer valid.Comment: 18 pages, 11 figures, one reference adde
Topology Change of Coalescing Black Holes on Eguchi-Hanson Space
We construct multi-black hole solutions in the five-dimensional
Einstein-Maxwell theory with a positive cosmological constant on the
Eguchi-Hanson space, which is an asymptotically locally Euclidean space. The
solutions describe the physical process such that two black holes with the
topology of S^3 coalesce into a single black hole with the topology of the lens
space L(2;1)=S^3/Z_2. We discuss how the area of the single black hole after
the coalescence depends on the topology of the horizon.Comment: 10 pages, Some comments are added. to be published as a letter in
Classical and Quantum Gravit
Search for anions in molecular sources: C4H- detection in L1527
We present the results of a search for the negative ion C4H- in various dark
clouds, low mass star-forming regions and photon-dominated regions (PDRs). We
have also searched for C6H-, C2H- and CN- in some of the sources. The
millimeter-wave observations were carried out with the IRAM-30m telescope. We
detect C4H-, through the J = 9-8 and J = 10-9 rotational transitions, in the
low mass star-forming region L1527. We thus confirm the tentative detection of
the J = 9-8 line recently reported toward this source. The [C4H-]/[C4H] ratio
found is 0.011 %, which is slightly lower than the value observed in IRC
+10216, 0.024 %, but above the 3 sigma upper limit we derive in TMC-1, < 0.0052
%. We have also derived an upper limit for the [C6H-]/[C6H] ratio in the
Horsehead Nebula, and for various anion-to-neutral ratios in the observed
sources. These results are compared with recent chemical models.Comment: 4 pages, 1 figure; accepted for A&A Letter
Mass and angular momenta of Kerr anti-de Sitter spacetimes in Einstein-Gauss-Bonnet theory
We compute the mass and angular momenta of rotating anti-de Sitter spacetimes
in Einstein-Gauss-Bonnet theory of gravity using a superpotential derived from
standard Noether identities. The calculation relies on the fact that the
Einstein and Einstein-Gauss-Bonnet vacuum equations are the same when
linearized on maximally symmetric backgrounds and uses the recently discovered
D-dimensional Kerr-anti-de Sitter solutions to Einstein's equations
Reissner-Nordstrom Black Holes and Thick Domain Walls
We solve numerically equations of motion for real self-interacting scalar
fields in the background of Reissner-Nordstrom black hole and obtained a
sequence of static axisymmetric solutions representing thick domain walls
charged black hole systems. In the case of extremal Reissner-Nordstrom black
hole solution we find that there is a parameter depending on the black hole
mass and the width of the domain wall which constitutes the upper limit for the
expulsion to occur.Comment: 18 pages, 10 figures, accepted for Phys. Rev.
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