Efficiency and Equilibrium when Preferences are Time-Inconsistent

We consider an exchange economy with time-inconsistent consumers whose preferences are additively separable. When these consumers trade in a sequence of markets, their time-inconsistency may introduce a non-convexity that gives them an incentive to trade lotteries. If there are many consumers, competitive equilibria with and without lotteries exist. The existence of symmetric equilibria may require lotteries. Symmetric equilibria that do not require lotteries are generically locally unique. Allocations that are Pareto efficient at the initial date are also renegotiation-proof. Competitive equilibria are Pareto efficient in this sense, and for generic endowments, if and only if preferences are locally homothetic. For non-homothetic preferences, the introduction of lottery markets has an ambiguous impact on the equilibrium welfare of consumers at the initial date.Dynamic inconsistency, competitive equilibrium, lotteries, generic inefficiency.

Manipulation of Choice Behavior

We introduce and study the problem of manipulation of choice behavior. In a class of two-stage models of decision making, with the agent's choices determined by three "psychological variables," we imagine that a subset of these variables can be selected by a "manipulator." To what extent does this confer control of the agent's behavior? Within the specified framework, which overlaps with two existing models of choice under cognitive constraints, we provide a complete answer to this question.attention, choice function, revealed preference, satisficing, threshold

Prospects of detecting gamma-ray emission from galaxy clusters: cosmic rays and dark matter annihilations

We study the possibility for detecting gamma-ray emission from galaxy clusters. We consider 1) leptophilic models of dark matter (DM) annihilation that include a Sommerfeld enhancement (SFE), 2) different representative benchmark models of supersymmetric DM, and 3) cosmic ray (CR) induced pion decay. Among all clusters/groups of a flux-limited X-ray sample, we predict Virgo, Fornax and M49 to be the brightest DM sources and find a particularly low CR-induced background for Fornax. For a minimum substructure mass given by the DM free-streaming scale, cluster halos maximize the substructure boost for which we find a factor above 1000. Since regions around the virial radius dominate the annihilation flux of substructures, the resulting surface brightness profiles are almost flat. This makes it very challenging to detect this flux with imaging atmospheric Cherenkov telescopes. Assuming cold dark matter with a substructure mass distribution down to an Earth mass and using extended Fermi upper limits, we rule out the leptophilic models in their present form in 28 clusters, and limit the boost from SFE in M49 and Fornax to be < 5. This corresponds to a limit on SFE in the Milky Way of < 3, which is too small to account for the increasing positron fraction with energy as seen by PAMELA and challenges the DM interpretation. Alternatively, if SFE is realized in Nature, this would imply a limiting substructure mass of M_lim > 10^4 M_sol - a problem for structure formation. Using individual cluster observations, it will be challenging for Fermi to constrain our selection of DM benchmark models without SFE. The Fermi upper limits are, however, closing in on our predictions for the CR flux using an analytic model based on cosmological hydrodynamical cluster simulations. We limit the CR-to-thermal pressure in nearby bright galaxy clusters of the Fermi sample to < 10% and in Norma and Coma to < 3%.Comment: 43 pages, 23 figures, 10 tables. Accepted for publication in Phys. Rev. D: streamlined paper, added a paragraph about detectability to introduction, few references added, and few typos correcte

Inferring cognitive heterogeneity from aggregate choices

Theories of bounded rationality often assume a rich dataset of choices from many overlapping menus, limiting their practical applicability. In contrast, we study the problem of identifying the distribution of cognitive characteristics in a population of agents from a minimal dataset that consists of aggregate choice shares from a single menu, and includes no observable covariates of any kind. With homogeneous preferences, we find that “consideration capacity” and “consideration probability” distributions can both be recovered effectively if the menu is sufficiently large. This remains true generically when tastes are heterogeneous with a known distribution. When the taste distribution is unknown, we show that joint choice share data from three “occasions” are generically sufficient for full identification of the cognitive distribution, and also provide substantial information about tastes

Inferring cognitive heterogeneity from aggregate choices

One potentially important drawback of existing theories of limited attention is that they typically assume a rich dataset of choices from many menus. We study the problem of identifying the distribution of cognitive characteristics in a population of agents when only aggregate choice behavior from a single menu is observable. We show how both “consideration probability” and “consideration capacity” distributions can be substantially identified by aggregate choice shares. We also suggest how to embed the attention models in an econometric specification of the inference problem. Finally, we sucessfully use our results to recover the true parameters in Monte Carlo simulations of both models

Patterns of Irregular Burials in Western Europe (1st-5th Century AD)

International audienceBackground :Irregular burials (IB-burials showing features that contrast with the majority of others in their geographic and chronological context) have been the focus of archaeological study because of their relative rarity and enigmatic appearance. Interpretations of IB often refer to supposed fear of the dead or to social processes taking place in time-specific contexts. However, a comprehensive and quantitative analysis of IB for various geographical contexts is still lacking, a fact that hampers any discussion of these burials on a larger scale. Methods :Here, we collected a bibliographic dataset of 375 IB from both Britain and Continental Europe, altogether spanning a time period from the 1st to the 5th century AD. Each burial has been coded according to ten dichotomous variables, further analyzed by means of chi-squared tests on absolute frequencies, non-metric multidimensional scaling, and cluster analysis. Results :Even acknowledging the limits of this study, and in particular the bias represented by the available literature, our results point to interesting patterns. Geographically, IB show a contrast between Britain and Continental Europe, possibly related to historical processes specific to these regions. Different types of IB (especially prone depositions and depositions with the cephalic extremity displaced) present a series of characteristics and associations between features that permit a more detailed conceptualization of these occurrences from a socio-cultural perspective that aids to elucidate their funerary meaning. Conclusions and Significance :Altogether, the present work stresses the variability of IB, and the need to contextualize them in a proper archaeological and historical context. It contributes to the discussion of IB by providing a specific geographic and chronological frame of reference that supports a series of hypotheses about the cultural processes possibly underlying their occurrence