The sense of rotation of subhaloes in cosmological dark matter haloes

We present a detailed analysis of the velocity distribution and orientation of orbits of subhaloes in high resolution cosmological simulations of dark matter haloes. We find a trend for substructure to preferentially revolve in the same direction as the sense of rotation of the host halo: there is an excess of prograde satellite haloes. Throughout our suite of nine host haloes (eight cluster sized objects and one galactic halo) there are on average 59% of the satellites corotating with the host. Even when including satellites out to five virial radii of the host, the signal still remains pointing out the relation of the signal with the infall pattern of subhaloes. However, the fraction of prograde satellites weakens to about 53% when observing the data along a (random) line-of-sight and deriving the distributions in a way an observer would infer them. This decrease in the observed prograde fraction has its origin in the technique used by the observer to determine the sense of rotation, which results in a possible misclassification of non-circular orbits. We conclude that the existence of satellites on corotating orbits is another prediction of the cold dark matter structure formation scenario, although there will be difficulties to verify it observationally. Since the galactic halo simulation gave the same result as the cluster-sized simulations, we assume that the fraction of prograde orbits is independent of the scale of the system, though more galactic simulations would be necessary to confirm this.Comment: 16 pages, 9 figures, accepted by MNRAS; extended comparison with previous work (mistake corrected) and observations, typos correcte

Five Indefinitely Repeated Games in the Laboratory

I experimentally test play in five indefinitely repeated games: a hawk-dove game, a game of chicken, a trust game, a coordination game, and a constant-sum game. I compare the different game histories that affect decision making in each of the games. Une étude expérimentale a été menée afin de tester les décisions prises lors de cinq jeux répétés où le nombre de répétitions est inconnu : un jeu de type hawk-dove, un jeu de type chicken, un jeu de confiance, un jeu de coordination et un jeu à somme constante. Les historiques des différents jeux sont comparés afin d’analyser les prises de décisions des participants dans chaque jeu.experimental economics, repeated games, économie expérimentale, jeux répétés

Learning-by-Doing in an Ambiguous Environment

We experimentally test whether risk aversion or ambiguity aversion can explain decisions in a learning-by-doing game. We first measure subjects' preferences toward risk and ambiguity, and then use these measures to predict behavior in the game. We find that ambiguity averse subjects pay more often to resolve ambiguity, and we find that less risk averse subjects earn more in the game. Our results, in light of a previous field study of farmers in a developing economy, provide further evidence of a link between ambiguity aversion and technology choice, as well as a link between risk aversion and farm profitability. Une étude expérimentale a été menée afin de tester si l’aversion au risque ou l’aversion à l’ambiguïté peuvent expliquer les décisions prises par les sujets lors d’un jeu d’apprentissage par essais. Nous avons d’abord mesuré la préférence des sujets face au risque et à l’ambiguïté, et avons ensuite utilisé ces mesures pour prédire le comportement des sujets au cours du jeu. Nous avons pu constater que les sujets qui éprouvent de l’aversion à l’ambiguïté décident de payer plus souvent afin de clarifier cette ambiguïté. D’autre part, nous avons constaté que moins les sujets éprouvent de l’aversion au risque, plus leurs gains lors du jeu sont élevés. À la lumière d’une étude sur le terrain ayant eu lieu avec des fermiers travaillant dans une économie en développement, nos résultats confirment l'évidence d'un lien entre l'aversion à l'ambiguïté et les choix technologiques, ainsi que d'un lien entre l'aversion au risque et la rentabilité d'une ferme.learning-by-doing, technology choice, risk preferences, risk measurement instruments, ambiguity aversion, experimental economics, apprentissage par essais, choix technologiques, préférences vis-à-vis du risque, instruments de mesure du risque, aversion à l’ambiguïté, économie expérimentale

Harnessing the Power of Focal Points To Measure Social Agreement

This paper reports results from an application of Thomas Schelling’s (1960) concept of a focal point to the measure of social agreement on the received tone of media content. In our experiments, subjects rate the tone, positive, negative, or neutral, of newspaper articles and news broadcasts, with an incentive to coordinate responses. We compare the content analysis of a traditional subject pool with those of a representative cross-section of the general public. Our application of the coordination game with strategy labels illustrates that the concept of a focal point can be put to use as a measure of social agreement. Le document présente les résultats obtenus en appliquant le concept de point focal, avancé par Thomas Schelling (1960), à la mesure de l’accord social concernant la perception du ton qui se dégage du contenu médiatique. Dans le cadre des expériences mises sur pied, les sujets évaluent le ton, positif, négatif ou neutre, adopté dans des articles de journaux et des bulletins de nouvelles et sont encouragés, par des mesures incitatives, à coordonner leurs réponses. Nous comparons l’analyse du contenu réalisée par un bassin traditionnel de sujets à celle menée par un échantillon représentatif du grand public. Notre application du jeu de coordination faisant appel à des étiquettes de stratégies démontre que la notion de point focal peut être utilisée pour mesurer l’accord social.Coordination, focal point, experiment, content analysis, media, Coordination, point focal, expérience, analyse du contenu, médias

A Simple Test of Learning Theory?

We report experiments designed to test the theoretical possibility, first discovered by Shapley (1964), that in some games learning fails to converge to any equilibrium, either in terms of marginal frequencies or of average play. Subjects played repeatedly in fixed pairings one of two 3 × 3 games, each having a unique Nash equilibrium in mixed strategies. The equilibrium of one game is predicted to be stable under learning, the other unstable, provided payoffs are sufficiently high. We ran each game in high and low payoff treatments. We find that, in all treatments, average play is close to equilibrium even though there are strong cycles present in the data.: Games, Learning, Experiments, Stochastic Fictitious Play, Mixed Strategy Equilibria.

AN EXPERIMENTAL TEST OF TAYLOR-TYPE RULES WITH INEXPERIENCED CENTRAL BANKERS

We experimentally test whether a class of monetary policy decision rules describes decision making in a population of inexperienced central bankers. In our experiments, subjects repeatedly set the short-term interest rate for a computer economy with inflation as their target. A large majority of subjects learn to successfully control inflation. We find that Taylor-type rules fit the choice data well, and are instrumental in characterizing heterogeneity in decision making. Our experiment is the first to begin to organize data experimentally with an eye on monetary policy rules for this, one of the most widely watched and analyzed decisions in economics.