An auction mechanism for public goods provision: an experimental study

We experiment a new mechanism for the provision of a discrete public good: in a fixed period individuals can contribute several times; at any moment they can see the total amount collected; at the end of the period, the public good is provided if the amount covers the cost. We find that the ability of the mechanism to provide efficiently the public good decreases with the amount of the provision cost.Public Goods, Experiments, Mechanism Design

The Individual Behavior in a Public Goods game

Generally, with a standard linear public goods game, one observes at the aggregate level that contributions lay between the Nash equilibrium and the social optimum and decrease over time with an end-effect.Our purpose is to see whether these general aggregate results remain available at the group and at the individual levels. To do so, we formed six groups of four persons and made them play a public goods game. At the aggregate level, we find that our results correspond almost to the standard experimental findings in literature.Using the classification of Isaac et al. (1984), we find that at the group level, only two groups adopt the standard behavior and only two groups present a behavior similar to what we obtain at the aggregate level. At the individual level, we compare contributions over time of each subject to the group and the aggregate results and classify them into types. Only in one of the 6 groups individuals adopt an homogeneous behavior. In the five other groups, individuals have different behaviors.Public Goods; Free-Riding; Aggregate level; Individual Behavior; Experiments.

Interior collective optimum in a volontary contribution to a public-goods game : an experimental approach

We run a public goods experiment with four different treatments. The payoff function is chosen such that the Nash equilibrium (NE) and the collective optimum (CO) are both in the interior of the strategy space. We test the effect of varying the level of the collective optimum on contributions. The results show that contributions increase with the level of the CO.Public goods, Experiments, interior solutions, social dilemma

Interior Collective Optimum in a Volontary Contribution to a Public-Goods Game : An Experimental Approach

We run a public good experiment with four different treatments. The payoff function is chosen such that the Nash equilibrium (NE) and the collective optimum (CO) are both in the interior of the strategy space. We try to test the effect of varying the level of the collective optimum, which changes the "social dilemma", involved in the decision as to how much to contribute to the public good . Our results show that contributions increase with the level of the interior CO. There is overcontribution in comparison to the NE and under contribution in comparison to the CO. But contributions are as far from the CO as the level of this former gets high. An overcontribution index that takes into account the effective contribution relative to both, the NE and the CO, shows that subjects adopt a constant behavior while passing from one treatment to another: they contribute a constant share of the CO.Public Goods, Experiments, Interior Solutions, Social Dilemma

The Emergence of Coordination in Public Good Games

In physical models it is well understood that the aggregate behaviour of a system is not in one to one correspondence with the behaviour of the average individual element of that system. Yet, in many economic models the behaviour of aggregates is thought of as corresponding to that of an individual. A typical example is that of public goods experiments. A systematic feature of such experiments is that, with repetition, people contribute less to public goods. A typical explanation is that people “learn to play Nash” or something approaching it. To justify such anexplanation, an individual learning model is tested on average or aggregate data. In this paper we will examine this idea by analysing average and individual behaviour in a series of public goods experiments. We analyse data from a series of games of contributions to public goods and firstly to see what happens, if we follow the standard approach and test a learning model on the average data. We then look at individual data, examine the changes that this produces and see if somegeneral model such as the EWA (Expected Weighted Attraction) with varying parameters can account for individual behaviour. We find that once we disaggregate data such models have poor explanatory power. Groups do not learn as supposed, their behaviour differs markedly from one group to another, and the behaviour of the individuals who make up the groups also varies within groups. The decline in aggregate contributions cannot be explained by resorting to a uniformmodel of individual behaviour.Experimental Economics; Public Goods; Learning models;Individual and Aggregate behaviour.

Dynamic voluntary contributions to a discrete public good: Experimental evidence.

Public Goods ; Experiments ; Voluntary contributions ; Dynamic contributions.

Dynamic voluntary contributions to a discrete public good:Experimental evidence

We experiment a mechanism for the provision of a discrete public good where individuals are allowed to update upwards their contribution during a fixed time interval. Experimental evidence shows that subjects increase their contributions in order to finance the cost of the good. The public good is financed more frequently when its cost is low relative to the social ability to pay.Public Goods; Experiments; Voluntary contributions; Dynamic contributions

Charged exctions in two-dimensional transition-metal dichalcogenides - semiclassical calculation of Berry-curvature effects

We theoretically study the role of the Berry curvature on neutral and charged excitons in two-dimensional transition-metal dichalcogenides. The Berry curvature arises due to a strong coupling between the conduction and valence bands in these materials that can to great extent be described within the model of massive Dirac fermions. The Berry curvature lifts the degeneracy of exciton states with opposite angular momentum. Using an electronic interaction that accounts for non-local screening effects, we find a Berry-curvature induced splitting of $\sim 17$ meV between the 2$p_{-}$ and 2$p_{+}$ exciton states in WS$_2$, consistent with experimental findings. Furthermore, we calculate the trion binding energies in WS$_2$ and WSe$_2$ for a large variety of screening lenghts and different dielectric constants for the environment. Our approach indicates the prominent role played by the Berry curvature along with non-local electronic interactions in the understanding of the energy spectra of neutral and charged excitons in transition-metal dichalcogenides and in the the interpretation of their optical properties.Comment: 11 pages, 3 figure

Hunger ‘beyond Appetite’ Nurture Dialect(ic)s in Toni Morrison’s Beloved

Nurture dialect(ic)s is a central motif in Toni Morrison’s Beloved (1987). From a cursory reading, the novel reveals the extent to which the African American experience of repression and dispersal is informed by the dialectics of hunger, cannibalism, and appropriation. Yet, a close reading of the narrative reveals that the dynamics of hunger and ingestion are mainly psychological and narratological. A thorough investigation of these dynamics invites an exploration of nurture imagery in the novel as well as its sociological, anthropological, historical and spatial inscriptions. This paper traces the various manifestations of the hunger/ingestion motif in Beloved and its implications at the psychological and diegetic levels, mapping out the connection between hunger and storytelling as a form of resistance. At a deeper level, however, the novel also evinces how the hunger/ingestion dialectics inform not only African Americans’ emotional and spiritual deprivation, but also the diegetic in(di)gestion, disadjustments, and dis(re)memberment of their history and identity. Through mapping out the fusion between the intra-diegetic and extra-diegetic, this essay ultimately argues that Morrison’s transgressive re-reading/re-writing of the imperial archive of black history and identity essentially requires both a visceral reliving of [its] trauma[s]” (Young 9) and a parodic o/aural and narratological reinscription of its predatory patterns.