L2-torsion of hyperbolic manifolds

The L^2-torsion is an invariant defined for compact L^2-acyclic manifolds of determinant class, for example odd dimensional hyperbolic manifolds. It was introduced by John Lott and Varghese Mathai and computed for hyperbolic manifolds in low dimensions. In this paper we show that the L^2-torsion of hyperbolic manifolds of arbitrary odd dimension does not vanish. This was conjectured by J. Lott and W. Lueck. Some concrete values are computed and an estimate of their growth with the dimension is given.Comment: AMS-LaTeX2e, 5 pages, to appear in Manuscripta Mathematic

Modelling airport and airline choice behaviour with the use of stated preference survey data

The majority of studies of air travel choice behavior make use of revealed preference (RP) data, generally in the form of survey data collected from departing passengers. While the use of RP data has certain methodological advantages over the use of stated preference (SP) data, major issues arise because of the often low quality of the data relating to the un-chosen alternatives, in terms of explanatory variables as well as availability. As such, studies using RP survey data often fail to recover a meaningful fare coefficient, and are generally not able to offer a treatment of the effects of airline allegiance. In this paper, we make use of SP data for airport and airline choice collected in the US in 2001. The analysis retrieves significant effects relating to factors such as airfare, access time, flight time and airline and airport allegiance, illustrating the advantages of SP data in this context. Additionally, the analysis explores the use of non-linear transforms of the explanatory variables, as well as the treatment of continuous variations in choice behavior across respondents

Systemorientierte Schulpsychologie

Systemorientierte Therapieformen auf das Feld der Schulpsychologie anzuwenden, bringt größere Schwierigkeiten mit sich als deren Anwendung in der ambulanten Kinder- und Jugendpsychologie und -psychiatrie, weil Schule und Familie dem relevanten System zugerechnet werden müssen. Der Autor postuliert, daß anstelle von testpsychologischen Untersuchungen und Übernahme von Entscheidungen durch den psychologischen Fachmann, Entscheidungsprozesse viel mehr im System Schule/Familie, also zwischen Eltern und Lehrern, unter Gesprächsleitung des Schulpsychologen, stattfinden sollen. Bei „schwierigen Schülern", deren Verhalten beeinflußt werden sollte, muß der Lehrer mit zum Beeinflussungssystem gerechnet und in die schulpsychologischen Interventionen einbezogen werden. Die Anwendung von Tests wird diskutiert. Anhand von zwei kurzen Beispielen wird systemisches Vorgehen aufgezeigt. Die Frage der Kompetenzen des Psychologen als Voraussetzung für systemisches Vorgehen in der Schulpsychologie wird gestreift. (DIPF/Orig.

The (After) Life-Cycle Theory of Religious Contributions

We construct and estimate an economic model of religious giving. We employ a dynamic consumer optimization model with mortality in which intra-temporal utility stems from both consumption and religious contributions. Individuals also decide how to allocate resources between religious contributions (which have both a this-life consumption value and an after-life investment value) and other consumption expenditures. If religious contributions do not have an after-life investment value, the ratio of contributions to consumption expenditures should be unrelated to the probability of death. However, if there is an investment value from religious giving, individuals should allocate a greater share of their income to religious contributions as their probability of death increases. We estimate the model using data from the Consumer Expenditure Survey on the consumption and religious contribution patterns of a repeated cross-section of households and of a synthetic cohort panel. We find strong evidence that individuals behave as if religious contributions have a value in the after-life, in a manner consistent with the after life-cycle model. The estimates of the structural parameters of the model also imply that while after-life investment considerations (i.e. impending death) are an important determinant of the life-cycle profile of religious contributions, within-life (i.e. religious consumption) factors pin down a household’s average level of religious contributions over a lifetime.god, life-cycle, consumption, religion, tithing

What Drives Users to Pay for Freemium Services? Examining People’s Willingness to Pay for Music Services

Freemium is intended to be a promising method that allows content providers to earn money now that Web 2.0 users feel entitled to free software. However, industries that use freemium, like the music industry, still struggle to cover their costs. Despite its practical relevance, no studies have investigated why customers are willing to pay for a service that can also be used for free. Based on the Theory of Planned Behavior, we developed a research model to identify antecedents of consumers’ intentions and attitudes towards the premium version of music services when a free version is available. The results of our survey with 157 participants show that using the free version has a negative impact on users’ intention to pay for the premium version. Our practical implications indicate that music service providers should focus on the premium product and introduce a time-limited freemium