14,201 research outputs found
On the physical interpretation of the delta=2 Tomimatsu-Sato solution
The physical properties of the Tomimatsu-Sato delta=2 spacetime are analyzed,
with emphasis on the issues of the negative mass distribution in this spacetime
and the origin of a massless ring singularity which are treated with the aid of
an equatorially asymmetric two-body configuration arising within the framework
of the analytically extended double-Kerr solution. As a by-product of this
analysis it is proved analytically that the Kerr spacetime with negative mass
always has a massless naked ring singularity off the symmetry axis accompanied
by a region with closed timelike curves, and it is also pointed out that the
Boyer-Lindquist coordinates in that case should be introduced in a different
manner than in the case of the Kerr solution with positive mass.Comment: 13 pages, 6 figures, submitted to Prog. Theor. Phy
General Relativistic Thermoelectric Effects in Superconductors
We discuss the general-relativistic contributions to occur in the
electromagnetic properties of a superconductor with a heat flow. The appearance
of general-relativistic contribution to the magnetic flux through a
superconducting thermoelectric bimetallic circuit is shown. A response of the
Josephson junctions to a heat flow is investigated in the general-relativistic
framework. Some gravitothermoelectric effects which are observable in the
superconducting state in the Earth's gravitational field are considered.Comment: 13 pages, 2 figure
Path Planning for Cooperative Routing of Air-Ground Vehicles
We consider a cooperative vehicle routing problem for surveillance and
reconnaissance missions with communication constraints between the vehicles. We
propose a framework which involves a ground vehicle and an aerial vehicle; the
vehicles travel cooperatively satisfying the communication limits, and visit a
set of targets. We present a mixed integer linear programming (MILP)
formulation and develop a branch-and-cut algorithm to solve the path planning
problem for the ground and air vehicles. The effectiveness of the proposed
approach is corroborated through extensive computational experiments on several
randomly generated instances
On some points-and-lines problems and configurations
We apply an old method for constructing points-and-lines configurations in
the plane to study some recent questions in incidence geometry.Comment: 14 pages, numerous figures of point-and-line configurations; to
appear in the Bezdek-50 special issue of Periodica Mathematica Hungaric
Kernel-phases for high-contrast detection beyond the resolution limit
The detection of high contrast companions at small angular separation appears
feasible in conventional direct images using the self-calibration properties of
interferometric observable quantities. In the high-Strehl regime, available
from space borne observatories and using AO in the mid-infrared, quantities
comparable to the closure-phase that are used with great success in
non-redundant masking inteferometry, can be extracted from direct images, even
taken with a redundant aperture. These new phase-noise immune observable
quantities, called Kernel-phases, are determined a-priori from the knowledge of
the geometry of the pupil only. Re-analysis of HST/NICMOS archive and other
ground based AO images, using this new Kernel-phase algorithm, demonstrates the
power of the method, and its ability to detect companions at the resolution
limit and beyond.Comment: 7 pages, 4 figures, 2011 SPIE conference proceeding
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