Stability of Closed Timelike Geodesics

The existence and stability under linear perturbations of closed timelike geodesics (CTGs) in Bonnor-Ward spacetime is studied in some detail. Regions where the CTG exist and are linearly stable are exhibited.Comment: 5 pages, REvTex, discussion added. PLA, in pres

Probability representation in quantum field theory

The recently proposed probability representation of quantum mechanics is generalized to quantum field theory. We introduce a probability distribution functional for field configurations and find an evolution equation for such a distribution. The connection to the time-dependent generating functional of Green's functions is elucidated and the classical limit is discussed

Variáveis relacionadas ao rendimento da incubação de ovos em matrizes de frangos de corte.

bitstream/item/58383/1/CUsersPiazzonDocuments246.pdfAcesso em: 13 jun. 2007

O poder organizacional é preditor da qualidade da tomada de decisão

The aim of this study was to analyze the links between power and the quality of decision. Participants were 50 employees from an organizational company, consisting of two groups (High-Power, N=24; Low-Power, N=26) based on the hierarchical power position in the organization. To evaluate the quality of the decisions, all participants performed tasks involving choice among several alternatives in two separated moments of the same day: in the morning (at the beginning of the workday) and late afternoon (at the end of the workday). Additional subjective measures (fatigue, alertness, effort) and skin conductance were obtained. Results indicated that having high power in the organization was related to making better decisions, over and above the subjective levels of fatigue, alertness, effort, and of physiological arousal. No effects of time-of-day were found on the decision making. Consistent with experimental research, having power facilitated decision making performance in an organizational context.info:eu-repo/semantics/publishedVersio

Digitalizing Circular Economy through Blockchains: The Blockchain Circular Economy Index

The integration of circular economy (CE) models into everyday contexts generates huge amount of data involved in goods tracking and tokenization procedures. The sector of blockchain platforms is extremely varied, and the choice of the proper technology is not easy. It is important that the selection is conducted consistently with respect to the CE models. With this study, we present a performance index named Blockchain Circular Economy Index (BCEI). BCEI, obtained through Multicriteria Decision Analysis and Analytic Hierarchy Process, aims to measure the suitability of blockchain platforms to the needs highlighted by a CE scenario. The present study is contextualized by comparing six blockchain platforms, for each of which, the related BCEI is calculated. The results of the analysis show that transaction fee and energy consumption are the two most critical parameters. In addition, the results show the lack of a leading blockchain technology in CE models. Thus, there is a market space that can be exploited given the growing interest in digital and sustainable issues

Experimental measurement of photothermal effect in Fabry-Perot cavities

We report the experimental observation of the photothermal effect. The measurements are performed by modulating the laser power absorbed by the mirrors of two high-finesse Fabry-Perot cavities. The results are very well described by a recently proposed theoretical model [M. Cerdonio, L. Conti, A. Heidmann and M. Pinard, Phys. Rev. D 63 (2001) 082003], confirming the correctness of such calculations. Our observations and quantitative characterization of the photothermal effect demonstrate its critical importance for high sensitivity interferometric displacement measurements, as those necessary for gravitational wave detection.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let

Switching of Magnetic Moments of Nanoparticles by Surface Acoustic Waves

We report evidence of the magnetization reversal in nanoparticles by surface acoustic waves (SAWs). The experimental system consists of isolated magnetite nanoparticles dispersed on a piezoelectric substrate. Magnetic relaxation from a saturated state becomes significantly enhanced in the presence of the SAW at a constant temperature of the substrate. The dependence of the relaxation on SAW power and frequency has been investigated. The effect is explained by the effective ac magnetic field generated by the SAW in the nanoparticles.Comment: Accepted in Europhysics Letter

Circular Orbits in Einstein-Gauss-Bonnet Gravity

The stability under radial and vertical perturbations of circular orbits associated to particles orbiting a spherically symmetric center of attraction is study in the context of the n-dimensional: Newtonian theory of gravitation, Einstein's general relativity, and Einstein-Gauss-Bonnet theory of gravitation. The presence of a cosmological constant is also considered. We find that this constant as well as the Gauss-Bonnet coupling constant are crucial to have stability for $n>4$.Comment: 11 pages, 4 figs, RevTex, Phys. Rev. D, in pres