Number of Least Area Planes in Gromov Hyperbolic 3-Spaces

We show that for a generic simple closed curve C in the asymptotic boundary of a Gromov hyperbolic 3-space with cocompact metric X, there exist a unique least area plane P in X with asymptotic boundary C. This result has interesting topological applications for constructions of canonical 2-dimensional objects in 3-manifolds

SOCIAL NETWORKS OF THE ITALIAN MAFIA; THE STRONG AND WEAK PARTS

In this paper, it is argued that well-built, social network system has enabled the Mafia to\ud reach a certain level of success through three main networks: members, local people, and\ud politicians. I assert that the role of the executive power of the state has been partially\ud supportive in this success. Moreover, this paper also concludes that to combat different\ud Mafia groups, it is essential to know their strong and weak parts. Consequently, it is found\ud that their well-built network system does not solely comprise of strong parts but that the\ud weak parts also exist, albeit, that they have not yet played a defective role in the resolution of\ud the Mafia. Therefore, this paper suggests that the illustration of both the strong and weak\ud parts of these networks can have prominent and assisting role in the combat against the\ud Mafia phenomenon in the future, either by strengthening the weak parts or by weakening the\ud strong parts of its networks

Business models and stock exchange performance : empirical evidence

In recent years stock exchanges have been increasingly diversifying their operations into related business areas such as derivatives trading, post-trading services and software sales. This trend can be observed most notably among profit-oriented trading venues. While the pursuit for diversification is likely to be driven by the attractiveness of these investment opportunities, it is yet an open question whether certain integration activities are also efficient, both from a social welfare and from the exchanges' perspective. Academic contributions so far analyzed different business models primarily from the social welfare perspective, whereas there is only little literature considering their impact on the exchange itself. By employing a panel data set of 28 stock exchanges for the years 1999-2003 we seek to shed light on this topic by comparing the factor productivity of exchanges with different business models. Our findings suggest three conclusions: (1) Integration activity comes at the cost of increased operational complexity which in some cases outweigh the potential synergies between related activities and therefore leads to technical inefficiencies and lower productivity growth. (2) We find no evidence that vertical integration is more efficient and productive than other business models. This finding could contribute to the ongoing discussion about the merits of vertical integration from a social welfare perspective. (3) The existence of a strong in-house IT-competence seems to be beneficial to overcome