Search results for "NULL"
showing 10 items of 396 documents
Covariant determination of the Weyl tensor geometry
2001
We give a covariant and deductive algorithm to determine, for every Petrov type, the geometric elements associated with the Weyl tensor: principal and other characteristic 2-forms, Debever null directions and canonical frames. We show the usefulness of these results by applying them in giving the explicit characterization of two families of metrics: static type I spacetimes and type III metrics with a hypersurface-orthogonal Killing vector. PACS numbers: 0240M, 0420C
On the invariant symmetries of the D-metrics
2007
We analyze the symmetries and other invariant qualities of the $\mathcal{D}$-metrics (type D aligned Einstein Maxwell solutions with cosmological constant whose Debever null principal directions determine shear-free geodesic null congruences). We recover some properties and deduce new ones about their isometry group and about their quadratic first integrals of the geodesic equation, and we analyze when these invariant symmetries characterize the family of metrics. We show that the subfamily of the Kerr-NUT solutions are those admitting a Papapetrou field aligned with the Weyl tensor.
Lorentzian Comments on Stokes Parameters
2003
The popular Stokes statements about polarized light are interpreted in a Minkowskian language using a Lorentzian representation for the Stokes parameters and the degree of polarization. The evolution equations for Stokes parameters on a curved space-time are obtained using the parallel transport of the polarization vector along a null geodesic. The interest of these equations in Astrophysics and Relativistic Cosmology is outlined.
Real-time low level feature extraction for on-board robot vision systems
2006
Robot vision systems notoriously require large computing capabilities, rarely available on physical devices. Robots have limited embedded hardware, and almost all sensory computation is delegated to remote machines. Emerging gigascale integration technologies offer the opportunity to explore alternative computing architectures that can deliver a significant boost to on-board computing when implemented in embedded, reconfigurable devices. This paper explores the mapping of low level feature extraction on one such architecture, the Georgia Tech SIMD Pixel Processor (SIMPil). The Fast Boundary Web Extraction (fBWE) algorithm is adapted and mapped on SIMPil as a fixed-point, data parallel imple…
Pointwise characterizations of Hardy-Sobolev functions
2006
We establish simple pointwise characterizations of functions in the Hardy-Sobolev spaces within the range n/(n+1)<p <=1. In addition, classical Hardy inequalities are extended to the case p <= 1.
Absolutely continuous functions in Rn
2005
Abstract For each 0 α 1 we consider a natural n-dimensional extension of the classical notion of absolute continuous function. We compare it with the Malý's and Hencl's definitions. It follows that each α-absolute continuous function is continuous, weak differentiable with gradient in L n , differentiable almost everywhere and satisfies the formula on change of variables.
Predicting the Significance of Necessity
2019
With Necessary Condition Analysis (NCA), a necessity effect is estimated by calculating the amount of empty space in the upper-left corner in a plot with a predictor X and an outcome Y, and recently a method for testing the statistical significance of the necessity effect through permutation has been proposed. In the present simulation study, this method was found to give significant results already with a very weak true population necessity effect, i.e., exhibit high power, unless the sample size is very small. However, in some situations the significance of the necessity effect tends to increase with increased degree of sufficiency, which is paradoxical for a method whose objective is to …
Notazioni brevi in tema di pregiudizialità tra processo canonico di nullità e azione civile di scioglimento del matrimonio
2009
Rapporti tra giurisdizione ecclesiastica e civile. Nullità del matrimonio canonico e divorzio civile. Sospensione per pregiudizialità.
Période suspecte. Action révocatoire du droit allemand exercée en France par un syndic allemand. Loi applicable
2013
International audience; (Com., 2 octobre 2012, n° 10-18.005, F. Schmitt ès qual. c/ M.Mialon, D. 2013. 62, note F. Jault-Seseke et D. Robine ; Com., 2 octobre 2012, n° 11-14.406, Decombas c/ F. Schmitt ès qual., D. 2012. 2386, obs. A. Lienhard ; ibid. 2013. 62, note F. Jault-Seseke et D. Robine ; JCP 2012. 1246, note F. Mélin, et 1428, n° 12, obs. Ph. Pétel ; Rev. proc. coll. 2012, comm. 191, note M. Menjucq)
General Statistical Framework for Quantitative Proteomics by Stable Isotope Labeling
2014
Pedro J. Navarro et al.