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Sep 23, 2013
09/13

by
J. J. Tobin; L. Hartmann; G. Furesz; M. Mateo; S. T. Megeath

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We present a kinematic study of the Orion Nebula Cluster based upon radial velocities measured by multi-fiber echelle spectroscopy at the 6.5 meter MMT and Magellan telescopes. Velocities are reported for 1613 stars, with multi-epoch data for 727 objects as part of our continuing effort to detect and analyze spectroscopic binaries. We confirm and extend the results of Furesz et al. showing that the ONC is not relaxed, consistent with its youth, and that the stars generally follow the...

Source: http://arxiv.org/abs/0903.2775v1

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49

Sep 23, 2013
09/13

by
Mark Wildon

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This paper presents a solution to the Knights and Spies Problem: In a room there are n people, each labelled with a unique number between 1 and n. A person may either be a knight or a spy. Knights always tell the truth, while spies may either lie or tell the truth, as they see fit. Each person in the room knows the identity of everyone else. Apart from this, all that is known is that strictly more knights than spies are present. Asking only questions of the form: `Person i, what is the identity...

Source: http://arxiv.org/abs/0903.2869v1

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32

Sep 21, 2013
09/13

by
A. Coley; S. Hervik; G. Papadopoulos; N. Pelavas

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Kundt spacetimes are of great importance in general relativity in 4 dimensions and have a number of topical applications in higher dimensions in the context of string theory. The degenerate Kundt spacetimes have many special and unique mathematical properties, including their invariant curvature structure and their holonomy structure. We provide a rigorous geometrical kinematical definition of the general Kundt spacetime in 4 dimensions; essentially a Kundt spacetime is defined as one admitting...

Source: http://arxiv.org/abs/0901.0394v2