62,477 research outputs found
On the topology of initial data sets with higher genus ends
In this note we study the topology of 3-dimensional initial data sets with
horizons of a sort associated with asymptotically locally anti-de Sitter
spacetimes. We show that, within this class, those initial data sets which
contain no (immersed) marginally outer trapped surfaces in their interior must
have simple topology: they are a product of a surface and an interval, or a
mild variation thereof, depending on the connectedness of the horizon and on
its genus relative to that of the end. The results obtained here extend results
in [11] to the case of higher genus ends.Comment: v2: 13 pages, 1 figure; minor corrections and changes, Lemma 2.2
added. To appear in Commun Math Phy
Grid Diagrams and Legendrian Lens Space Links
Grid diagrams encode useful geometric information about knots in S^3. In
particular, they can be used to combinatorially define the knot Floer homology
of a knot K in S^3, and they have a straightforward connection to Legendrian
representatives of K in (S^3, \xi_\st), where \xi_\st is the standard, tight
contact structure. The definition of a grid diagram was extended to include a
description for links in all lens spaces, resulting in a combinatorial
description of the knot Floer homology of a knot K in L(p, q) for all p > 0. In
the present article, we explore the connection between lens space grid diagrams
and the contact topology of a lens space. Our hope is that an understanding of
grid diagrams from this point of view will lead to new approaches to the Berge
conjecture, which claims to classify all knots in S^3 upon which surgery yields
a lens space.Comment: 27 pages, 20 figure
Bidirectional step torque filter with zero backlash characteristic Patent
Gearing system for eliminating backlash and filtering input torque fluctuations from high inertia loa
An Early Bronze Age 'dagger grave' from Rameldry Farm, near Kingskettle, Fife
In February 2000, ploughing disturbed the capstone of a cist, located on the side of a prominent knowe at Rameldry Farm, near Kingskettle in central Fife. Excavation by Headland Archaeology Ltd on behalf of Historic Scotland revealed a short cist which contained the crouched inhumation of a man aged 40-50, who had suffered from arthritis, some tooth loss and possibly Paget's Disease. He had been buried wearing a garment adorned with six V-pelforated buttons. Five of these are of Whitby jet (including one with unique decoration including inlaid tin); the sixth is of the mineral lizardite, and has an enigmatic coating, possibly a glaze. Behind his shoulder was a dagger, of 'Milston type (East Kennet variant) it had had a fancy horn hilt and a scabbard lined with animal skin. The scabbard yielded two A MS radiocarbon dates, with a mean value of 2280-1970 cal Bc at 2
Ignition of binary alloys of uranium
Experiments determine the effect of alloying additives on the ignition of uranium. Data on oxidation rates, ignition temperatures, and burning curves are provided in the report
Graphics and composite material computer program enhancements for SPAR
User documentation is provided for additional computer programs developed for use in conjunction with SPAR. These programs plot digital data, simplify input for composite material section properties, and compute lamina stresses and strains. Sample problems are presented including execution procedures, program input, and graphical output
Exciton-polaron complexes in pulsed electrically-detected magnetic resonance
Several microscopic pathways have been proposed to explain the large magnetic
effects observed in organic semiconductors, but identifying and characterising
which microscopic process actually influences the overall magnetic field
response is challenging. Pulsed electrically-detected magnetic resonance
provides an ideal platform for this task as it intrinsically monitors the
charge carriers of interest and provides dynamical information which is
inaccessible through conventional magnetoconductance measurements. Here we
develop a general time domain theory to describe the spin-dependent reaction of
exciton-charge complexes following the coherent manipulation of paramagnetic
centers through electron spin resonance. A general Hamiltonian is treated, and
it is shown that the transition frequencies and resonance positions of the
exciton-polaron complex can be used to estimate inter-species coupling. This
work also provides a general formalism for analysing multi-pulse experiments
which can be used to extract relaxation and transport rates
Simultaneous chromatic dispersion, polarization-mode-dispersion and OSNR monitoring at 40Gbit/s
A novel method for independent and simultaneous monitoring of chromatic dispersion ( CD), first-order PMD and OSNR in 40Gbit/s systems is proposed and demonstrated. This is performed using in-band tone monitoring of 5GHz, optically down-converted to a low intermediate-frequency (IF) of 10kHz. The measurement provides a large monitoring range with good accuracies for CD (4742 +/- 100ps/nm), differential group delay (DGD) (200 +/- 4ps) and OSNR (23 +/- 1dB), independently of the bit-rate. In addition, the use of electro-absorption modulators (EAM) for the simultaneous down-conversion of all channels and the use of low-speed detectors makes it cost effective for multi-channel operation. (C) 2008 Optical Society of Americ
Stable divisorial gonality is in NP
Divisorial gonality and stable divisorial gonality are graph parameters,
which have an origin in algebraic geometry. Divisorial gonality of a connected
graph can be defined with help of a chip firing game on . The stable
divisorial gonality of is the minimum divisorial gonality over all
subdivisions of edges of .
In this paper we prove that deciding whether a given connected graph has
stable divisorial gonality at most a given integer belongs to the class NP.
Combined with the result that (stable) divisorial gonality is NP-hard by
Gijswijt, we obtain that stable divisorial gonality is NP-complete. The proof
consist of a partial certificate that can be verified by solving an Integer
Linear Programming instance. As a corollary, we have that the number of
subdivisions needed for minimum stable divisorial gonality of a graph with
vertices is bounded by for a polynomial
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