9,020 research outputs found
When Greenberger, Horne and Zeilinger meet Wigner's Friend
A general argument is presented against relativistic, unitary, single-outcome
quantum mechanics. This is achieved by combining the Wigner's Friend thought
experiment with measurements on a Greenberger-Horne-Zeilinger (GHZ) state, and
describing the evolution of the quantum state in various inertial frames.
Assuming unitary quantum mechanics and single outcomes, the result is that the
Born rule must be violated in some inertial frame: in that frame, outcomes are
obtained for which no corresponding term exists in the pre-measurement
wavefunction.Comment: 16 pages, 1 figur
AM CVn stars
I review our observational and theoretical knowledge of AM CVn stars,
focusing on recent developments. These include newly discovered systems, the
possibility that two recently discovered extremely short period objects are AM
CVn stars and an update on X-ray, UV an optical studies. Theoretical advances
include the study of the details of both the donor and accretor, and the
physics of the helium accretion discs. I review our (limited) knowledge of the
formation of AM CVn stars and the apparent success of the now more than 25 year
old suggestion that in these objects the mass transfer is driven by
gravitational wave radiation losses. The exciting prospect of directly
detecting these gravitational waves and the possibilities this brings conclude
this contribution.Comment: Error in table 1 corrected: orbital period GP Com is 2794 sec. Review
to appear in "The astrophysics of cataclysmic variables and related objects",
ASP Conf. Ser.,eds. J.M. Hameury and J.P. Lasot
Using Canonical Forms for Isomorphism Reduction in Graph-based Model Checking
Graph isomorphism checking can be used in graph-based model checking to achieve symmetry reduction. Instead of one-to-one comparing the graph representations of states, canonical forms of state graphs can be computed. These canonical forms can be used to store and compare states. However, computing a canonical form for a graph is computationally expensive. Whether computing a canonical representation for states and reducing the state space is more efficient than using canonical hashcodes for states and comparing states one-to-one is not a priori clear. In this paper these approaches to isomorphism reduction are described and a preliminary comparison is presented for checking isomorphism of pairs of graphs. An existing algorithm that does not compute a canonical form performs better that tools that do for graphs that are used in graph-based model checking. Computing canonical forms seems to scale better for larger graphs
Subnanometer Translation of Microelectromechanical Systems Measured by Discrete Fourier Analysis of CCD Images
AbstractâIn-plane linear displacements of microelectromechanical systems are measured with subnanometer accuracy by observing the periodic micropatterns with a charge-coupled device camera attached to an optical microscope. The translation of the microstructure is retrieved from the video by phase-shift computation using discrete Fourier transform analysis. This approach is validated through measurements on silicon devices featuring steep-sided periodic microstructures. The results are consistent with the electrical readout of a bulk micromachined capacitive sensor, demonstrating the suitability of this technique for both calibration and sensing. Using a vibration isolation table, a standard deviation of Ï = 0.13 nm could be achieved, enabling a measurement resolution of 0.5 nm (4Ï) and a subpixel resolution better than 1/100 pixel. [2010-0170
EUCARD magnet development
The FP7-EuCARD work package 7 (WP7), "HFM: Superconducting High Field Magnets
for higher luminosities and energies" is a collaboration between 12 European
institutes and firms with the objective of developing high field magnet
technology. WP7 foresees to construct a 13 T dipole with a 100 mm aperture, a B
= 6 T high temperature superconductor (HTS) dipole insert, a superconducting
HTS link and a superconducting helical undulator.Comment: 5 pages, contribution to the EuCARD-AccNet-EuroLumi Workshop: The
High-Energy Large Hadron Collider, Malta, 14 -- 16 Oct 2010; CERN Yellow
Report CERN-2011-003, pp. 45-4
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