Third rank Killing tensors in general relativity. The (1+1)-dimensional case

Third rank Killing tensors in (1+1)-dimensional geometries are investigated and classified. It is found that a necessary and sufficient condition for such a geometry to admit a third rank Killing tensor can always be formulated as a quadratic PDE, of order three or lower, in a Kahler type potential for the metric. This is in contrast to the case of first and second rank Killing tensors for which the integrability condition is a linear PDE. The motivation for studying higher rank Killing tensors in (1+1)-geometries, is the fact that exact solutions of the Einstein equations are often associated with a first or second rank Killing tensor symmetry in the geodesic flow formulation of the dynamics. This is in particular true for the many models of interest for which this formulation is (1+1)-dimensional, where just one additional constant of motion suffices for complete integrability. We show that new exact solutions can be found by classifying geometries admitting higher rank Killing tensors.Comment: 16 pages, LaTe

Asymptotic Entanglement Dynamics and Geometry of Quantum States

A given dynamics for a composite quantum system can exhibit several distinct properties for the asymptotic entanglement behavior, like entanglement sudden death, asymptotic death of entanglement, sudden birth of entanglement, etc. A classification of the possible situations was given in [M. O. Terra Cunha, {\emph{New J. Phys}} {\bf{9}}, 237 (2007)] but for some classes there were no known examples. In this work we give a better classification for the possibile relaxing dynamics at the light of the geometry of their set of asymptotic states and give explicit examples for all the classes. Although the classification is completely general, in the search of examples it is sufficient to use two qubits with dynamics given by differential equations in Lindblad form (some of them non-autonomous). We also investigate, in each case, the probabilities to find each possible behavior for random initial states.Comment: 9 pages, 2 figures; revised version accepted for publication in J. Phys. A: Math. Theo

The structure of the QED-Vacuum and Electron-Positron Pair Production in Super-Intense, pulsed Laser Fields

We discuss electron-positron pair-production by super-intense, short laser pulses off the physical vacuum state locally deformed by (stripped) nuclei with large nuclear charges. Consequences of non-perturbative vacuum polarisation resulting from such a deformation are shortly broached. Production probabilities per pulse are calculated.Comment: 10 pages, 1 figure, submitted to Journal of Physics

The skill paradox: Explaining and reducing employment discrimination against skilled immigrants

Using a social identity theory approach, we theorized that recruiters might be particularly biased against skilled immigrant applicants. We refer to this phenomenon as a skill paradox, according to which immigrants are more likely to be targets of employment discrimination the more skilled they are. Furthermore, building on the common ingroup identity model, we proposed that this paradox can be resolved through human resource management (HRM) strategies that promote inclusive hiring practices (e.g., by emphasizing fit with a diverse clientele). The results from a laboratory experiment were consistent with our predictions: Local recruiters preferred skilled local applicants over skilled immigrant applicants, but only when these applicants were qualified for a specific job. This bias against qualified and skilled immigrant applicants was attenuated when fit with a diverse clientele was emphasized, but not when fit with a homogeneous clientele was emphasized or when the hiring strategy was not explained. We discuss the implications of our findings for research on employment discrimination against skilled immigrants, including the role of inclusiveness for reducing discriminatory biases

Impacts of Extension Education on Improving Residential Stormwater Quality: Monitoring Results

The project reported in this article evaluated whether stormwater quality could be improved by educating homeowners and implementing best management practices in a suburban neighborhood. Nitrogen, phosphorus, and bacteria levels from two watersheds were compared using the paired watershed approach. Resident surveys, property site assessments, soil tests, and water quality and quantity monitoring were conducted. A x2-analysis of survey data indicated no significant changes in measured behavior. Significant (p=0.01) reductions in NO3-N and fecal coliform bacteria concentrations occurred; however, total nitrogen concentrations did not change significantly

Edge-Based Compartmental Modeling for Infectious Disease Spread Part III: Disease and Population Structure

We consider the edge-based compartmental models for infectious disease spread introduced in Part I. These models allow us to consider standard SIR diseases spreading in random populations. In this paper we show how to handle deviations of the disease or population from the simplistic assumptions of Part I. We allow the population to have structure due to effects such as demographic detail or multiple types of risk behavior the disease to have more complicated natural history. We introduce these modifications in the static network context, though it is straightforward to incorporate them into dynamic networks. We also consider serosorting, which requires using the dynamic network models. The basic methods we use to derive these generalizations are widely applicable, and so it is straightforward to introduce many other generalizations not considered here

Emergence of influential spreaders in modified rumor models

The burst in the use of online social networks over the last decade has provided evidence that current rumor spreading models miss some fundamental ingredients in order to reproduce how information is disseminated. In particular, recent literature has revealed that these models fail to reproduce the fact that some nodes in a network have an influential role when it comes to spread a piece of information. In this work, we introduce two mechanisms with the aim of filling the gap between theoretical and experimental results. The first model introduces the assumption that spreaders are not always active whereas the second model considers the possibility that an ignorant is not interested in spreading the rumor. In both cases, results from numerical simulations show a higher adhesion to real data than classical rumor spreading models. Our results shed some light on the mechanisms underlying the spreading of information and ideas in large social systems and pave the way for more realistic diffusion models.Comment: 14 Pages, 6 figures, accepted for publication in Journal of Statistical Physic