DEMOGRAPHIC TRANSITION IN EUROPE

Using panel cointegration analysis, we show that a cointegration relationship exists among fertility choice, infant mortality, real wages and real per capita output. The results suggest that in low mortality economies reductions in infant mortality will decrease fertility.

Interaction of the Particle with the String in Pole-Dipole Approximation

Within the framework of generalized Papapetrou method, we derive the effective equations of motion for a string with two particles attached to its ends, along with appropriate boundary conditions. The equations of motion are the usual Nambu-Goto-like equations, while boundary conditions turn out to be equations of motion for the particles at the string ends. The form of those equations is discussed, and they are explicitly solved for a particular case of a straight-line string rotating around its center. From this solution we obtain the correction terms to the $J\propto E^2$ law describing Regge trajectories, due to nonzero angular momenta of the particles.Comment: Proceedings of the BW2007 conference, 5 page

Weyl Card Diagrams and New S-brane Solutions of Gravity

We construct a new card diagram which accurately draws Weyl spacetimes and represents their global spacetime structure, singularities, horizons and null infinity. As examples we systematically discuss properties of a variety of solutions including black holes as well as recent and new time-dependent gravity solutions which fall under the S-brane class. The new time-dependent Weyl solutions include S-dihole universes, infinite arrays and complexified multi-rod solutions. Among the interesting features of these new solutions is that they have near horizon scaling limits and describe the decay of unstable objects.Comment: 78 pages, 32 figures. v2 added referenc

Weyl-type Fields with Geodesic Lines of Force

The static electrogravitational equations are studied and it is shown that an aligned type D metric which has a Weyl-type relationship between the gravitational and electric potential has shearfree geodesic lines of force. All such fields are then found and turn out to be the fields of a charged sphere, charged infinite rod and charged infinite plate. A further solution is also found with shearing geodesic lines of force. This new solution can have $m>|e|$ or $m<|e|$, but cannot be in the Majumdar-Papapetrou class (in which $m = |e|$). It is algebraically general and has flat equipotential surfaces.Comment: 13 pages, RevTe

Inferring offline hierarchical ties from online social networks

Social networks can represent many different types of relationships between actors, some explicit and some implicit. For example, email communications between users may be represented explicitly in a network, while managerial relationships may not. In this paper we focus on analyzing explicit interactions among actors in order to detect hierarchical social relationships that may be implicit. We start by employing three well-known ranking-based methods, PageRank, Degree Centrality, and Rooted-PageRank (RPR) to infer such implicit relationships from interactions between actors. Then we propose two novel approaches which take into account the time-dimension of interactions in the process of detecting hierarchical ties. We experiment on two datasets, the Enron email dataset to infer manager-subordinate relationships from email exchanges, and a scientific publication co-authorship dataset to detect PhD advisor-advisee relationships from paper co-authorships. Our experiments show that time-based methods perform considerably better than ranking-based methods. In the Enron dataset, they detect 48% of manager-subordinate ties versus 32% found by Rooted-PageRank. Similarly, in co-author dataset, they detect 62% of advisor-advisee ties compared to only 39% by Rooted-PageRank

Polixeni Papapetrou

Artist, Polixeni Papapetrou, discusses her photographic work