Chern-Simons Gravity in Four Dimensions

Five dimensional Chern-Simons theory with (anti-)de Sitter SO(1,5) or SO(2,4) gauge invariance presents an alternative to General Relativity with cosmological constant. We consider the zero-modes of its Kaluza-Klein compactification to four dimensions. Solutions with vanishing torsion are obtained in the cases of a spherically symmetric 3-space and of a homogeneous and isotropic 3-space, which reproduce the Schwarzshild-de Sitter and $\Lambda$CDM cosmological solutions of General Relativity. We also check that vanishing torsion is a stable feature of the solutions.Comment: 25 pages, Late

Behaviour of Charged Spinning Massless Particles

We revisit the classical theory of a relativistic massless charged point particle with spin and interacting with an external electromagnetic field. In particular, we give a proper definition of its kinetic energy and its total energy, the latter being conserved when the external field is stationary. We also write the conservation laws for the linear and angular momenta. Finally, we find that the particle's velocity may differ from $c$ as a result of the spin---electromagnetic field interaction, without jeopardizing Lorentz invariance.Comment: PDFtex file, 20 pages, 3 figures Revised version published in Symmetry (Basel

Monitoring the Accuracy of Multiple Occupancy Forecasts

Corporate executives closely monitor the accuracy of their hotels\u27 occupancy fore- casts since important decisions are based upon these predictions. This study lists the criteria for selecting an appropriate error measure. It discusses several evaluation methods focusing on statistical significance tests and demonstrates the use of two adequate evaluation methods: Mincer- Zamowitz\u27s efficiency test and Wilcoxon\u27s Non-Parametric Matched-Pairs Signed- Ranks test

A Topological-like Model for Gravity in 4D Space-time

In this paper we consider a model for gravity in 4-dimensional space-time originally proposed by Chamseddine, which may be derived by dimensional reduction and truncation from a 5-dimensional Chern-Simons theory. Its topological origin makes it an interesting candidate for an easier quantization, e.g., in the Loop Quantization framework. The present paper is dedicated to a classical analysis of the model's properties. Cosmological solutions as well as wave solutions are found and compared with the corresponding solutions of Einstein's General Relativity with cosmological constant.Comment: 24 pages, 2 figures, PDFLatex. Typos corrected. Subsection 2.2.1 is new and subsection 2.2.3 (old subsection 2.2.2) has been improve

Solid-phase microextraction of benzophenones coupled with gas chromatography analysis

Abstract. In this study, solid-phase microextraction  method combines with gas chromatography-flame ionization detector. The proposed method is used for the preconcentration of some benzophenones. Influence of different factors on the efficiency of extraction is described in detail. The analytical procedure was optimized for fiber coating selection, extraction time, temperature, sample pH, ionic strength. For all benzophenones, the highest enrichment factors were achieved using carboxen/polydimethylsiloxane/divinylbenzene fibre immersed directly into the water samples, containing 100 mg/mL of sodium chloride, at room temperature. The optimum pH range is 5.0 – 7.0. The relative standard deviations (RSDs) were from 1.3 to 10.0 % (n = 3). The method was applied to the determination of benzophenone, benzophenone-3, 2-hydroxybenzophenone in the lake water and urine.

Tracking people in crowds by a part matching approach

The major difficulty in human tracking is the problem raised by challenging occlusions where the target person is repeatedly and extensively occluded by either the background or another moving object. These types of occlusions may cause significant changes in the person's shape, appearance or motion, thus making the data association problem extremely difficult to solve. Unlike most of the existing methods for human tracking that handle occlusions by data association of the complete human body, in this paper we propose a method that tracks people under challenging spatial occlusions based on body part tracking. The human model we propose consists of five body parts with six degrees of freedom and each part is represented by a rich set of features. The tracking is solved using a layered data association approach, direct comparison between features (feature layer) and subsequently matching between parts of the same bodies (part layer) lead to a final decision for the global match (global layer). Experimental results have confirmed the effectiveness of the proposed method. © 2008 IEEE