3D-simulation of the Outer Convection-zone of an A-star

The convection code of Nordlund & Stein has been used to evaluate the 3D, radiation-coupled convection in a stellar atmosphere with Teff=7300K, logg=4.3 and [Fe/H]=0.0, corresponding to a main-sequence A9-star. I will present preliminary comparisons between the 3D-simulation and a conventional 1D stellar structure calculation, and elaborate on the consequences of the differences.Comment: 6 pages, 2 figures to appear in "The A Star Puzzle", IAU Symp. 224, J. Zverko, W. W. Weiss, J. Ziznovsky & S. J. Adelman eds., Cambridge Univ. Pres

Efficient Contracts for Digital Content

This paper analyses efficient contracts for digital content, focusing on the music industry. It contributes to the quest for an efficient intellectual property rights environment for information goods. Moreover, it adds an interesting application to the field of behavioural economics. The model is set in a contract theory framework with the copyright holder being the principal and a consumer the agent. We offer three contract cases for analysis: strong copy protection, a strategically low price and voluntary reciprocal contributions. Insights from the economics of information and behavioural economics - information goods have public goods properties; social preferences are significant among individuals - are applied to examine the value of a strict copyright enforcement in the digital age. We find that endogenous incomplete contracts based on fair, reciprocal behaviour may achieve a first-best allocation of information goods, while complete contracts are limited to second-best results.internet, music industry, social preferences, reciprocity, moral hazard, file sharing

Why Consumers Pay Voluntarily: Evidence from Online Music

Customers at the online music label Magnatune can pay what they want for albums, as long as the payment is within a given price range ($5-$18). Magnatune recommends to pay $8, and on average customers paid$8.20 (Regner and Barria, 2009). We ran an online survey and collected responses from 227 frequent Magnatune customers to gain insights about the underlying motivations to pay more than necessary. We control for individual response- and sample selection-bias, and find that reciprocity and guilt appear to be the major drivers for generous voluntary payments. Being inclined to follow social norms is a positive determinant for payments around the recommended price.social preferences, other-regarding behaviour, music industry, reciprocity, guilt, social norms, altruism, fairness, social-image concerns, survey

The Mass Mixing Length in Convective Stellar Envelopes

The scale length over which convection mixes mass in a star can be calculated as the inverse of the vertical derivative of the unidirectional (up or down) mass flux. This is related to the mixing length in the mixing length theory of stellar convection. We give the ratio of mass mixing length to pressure scale height for a grid of 3D surface convection simulations, covering from 4300\,K to 6900\,K on the main-sequence, and up to giants at $\log g = 2.2$, all for solar composition. These simulations also confirm what is already known from solar simulations, that convection doesn't proceed by discrete convective elements, but rather as a continuous, slow, smooth, warm upflow and turbulent, entropy deficient, fast down drafts. This convective topology also results in mixing on a scale as that of the classic mixing length formulation, and is simply a consequence of mass conservation on flows in a stratified atmosphere.Comment: 14 pages, 6 figures, accepted for publication in Ap

A note on the relationship between television viewing and individual happiness

In a recently published article, Bruni and Stanca (2008) suggest that television viewing has a negative impact on life satisfaction. In this note we argue that the empirical approach they use (an approach that omits the main effect of TV viewing in life satisfaction) is problematic. We estimate a microeconomic life satisfaction function and find mixed support for the claim that television viewing in general has a negative impact on individual happiness. Using a large cross-country comparison we find that there is a substantial heterogeneity across countries, which needs to be taken into account when concluding about television's effect on life satisfaction.Relational goods, Subjective well-being, TV consumption, Happiness

Other-regarding behaviour: Testing guilt- and reciprocity-based models

We analyse two types of belief-dependant models of social preferences: guilt aversion and reciprocity. In particular, we test the relevance of their input variables (second-order beliefs and general dispositions for guilt/reciprocity). The data confirm the predictions of belief-dependant models. Both second-order beliefs and a participant's sensitivity to guilt/reciprocity are relevant for the decisions taken. Second-order beliefs appear to have an inverse U-shaped effect on the extent of kind behaviour.social preferences, other-regarding behaviour, belief-dependent models, experiments, trust game, guilt aversion, beliefs, psychological game theory, emotions, reciprocity

Why Voluntary Contributions? Google Answers

We study the pricing and tipping behaviour of users of the online service `Google Answers'. While they set a price for the answer to their question ex ante, they can additionally give a tip to the researcher ex post. We develop a model that is based on reciprocal theories of social preferences pioneered by Rabin (1993) and extended by Dufwenberg and Kirchsteiger (2004). The predictions of our model are empirically tested with the field data we obtained. The reasons for leaving a tip are analysed. A significant amount of users are motivated by social preferences. We also find strong support for reputation concerns. Moreover, researchers appear to adjust their effort based on the user's previous tipping behaviour. We conclude that an endogenous incomplete contracts design encourages people to contribute voluntarily. This is motivated by reciprocity when people are socially minded, but also generally by strategic behaviour to build up a good reputation. Efficiency is increased when contracts are left open deliberately as high effort is sustained.social preferences, reciprocity, moral hazard, reputation, internet