Failure to collude in the presence of asymmetric information

In this paper, we design the optimal contract when two agents can collude under asymmetric information. They have correlated types, produce complementary inputs and are protected by limited liability. Therefore, a joint manipulation of reports allows them to internalize informational and productive externalities. We show that by taking advantage of the transaction costs created by asymmetric information, even though they collude, the principal can achieve the outcome without collusion regardless of the sign and the degree of correlation. In particular, the principal can implement a non-monotonic quantity schedule in a collusion-proof way while this is impossible if collusion occurs under complete information.

Optimal law enforcement under asymmetric information

In this paper, we focus on the problem created by asymmetric informationabout the enforcer's (agent's) costs associated to enforcement expenditure. This adverse selection problem affects optimal law enforcement because a low cost enforcer may conceal its information by imitating a high cost enforcer, and must then be given a compensation to be induced to reveal its true costs. The government faces a trade-off between minimizing the enforcer's compensation and maximizing the net surplus of harmful acts. As a consequence, the probability of apprehension and punishment is usually reduced leading to more offenses being committed. We show that asymmetry of information does not affect law enforcement as long as raising public funds is costless. The consideration of costly raising of public funds permits to establish the positive correlation between asymmetry of information between government and enforcers andthe crime rate.

Mechanisms of spindle positioning during "Caenorhabditis elgans" asymmetric cell division

Résumé : Le positionnement correct du fuseau mitotique est crucial pour les divisions cellulaires asymétriques, car il gouverne le contrôle spatial de la division cellulaire et assure la ségrégation adéquate des déterminants cellulaires. Malgré leur importance, les mécanismes contrôlant le positionnement du fuseau mitotique sont encore mal compris. Chez l'embryon au stade une-cellule du nématode Caenorhabditis elegans, le fuseau mitotique est positionné de manière asymétrique durant l'anaphase grâce à l'action de générateurs de force situés au cortex cellulaire, et dont la nature était jusqu'alors indéterminée. Ces générateurs de force corticaux exercent une traction sur les microtubules astraux et sont dépendants de deux protéines Gα et de leurs protéines associées. Cette thèse traite de la nature de la machinerie responsable pour la génération des forces de tractions, ainsi que de son lien avec les protéines Gα et associées. Nous avons combiné des expériences de coupure par faisceau laser du fuseau mitotique avec le contrôle temporel de l'inactivation de gènes ou de l'exposition à des produits pharmacologiques. De cette manière, nous avons établi que la dynéine, un moteur se déplaçant vers l'extrémité négative des microtubules, ainsi que la dynamique des microtubules, sont toutes deux requises pour la génération efficace des forces de tractions. Nous avons démontré que les protéines Gα et leurs protéines associées GPR-1/2 et LIN-5 interagissent in vivo avec LIS-1, un composant du complexe de la dynéine. De plus, nous avons découvert que les protéines Gα, GPR-1/2 et LIN-5 promeuvent la présence du complexe de la dynéine au cortex cellulaire. Nos résultats suggèrent un mécanisme par lequel les protéines Gα permettent le recrutement cortical de GPR-1/2 et LIN-5, assurant ainsi la présence de la dynéine au cortex. Conjointement avec la dynamique des microtubules, ce mécanisme permet la génération des forces de tractions afin d'obtenir une division cellulaire correcte. Comme les mécanismes contrôlant le positionnement du fuseau mitotique et les divisions cellulaires asymétriques sont conservés au cours de l'évolution, nous espérons que les mécanismes élucidés par ce travail sont d'importance générale pour la génération de la diversité cellulaire durant le développement. De plus, ces mécanismes pourraient être applicables à d'autres divisions asymétriques, comme celle des cellules souches, dont le disfonctionnement peut entraîner la génération de cellules cancéreuses. Abstract : Proper spindle positioning is crucial for asymmetric cell division, because it controls spatial aspects of cell division and the correct inheritance of cell-fate determinants. However, the mechanisms governing spindle positioning remain incompletely understood. In the Caenorhabditis elegans one-cell stage embryo, the spindle becomes asymmetrically positioned during anaphase through the action of as-yet unidentified cortical force generators that pull on astral microtubules and that depend on two Gα proteins and associated proteins. This thesis addresses the nature of the force generation machinery and the link with the Gα and associated proteins. By performing spindle-severing experiments following temporally restricted gene inactivation and drug exposure, we established that microtubule dynamics and the minus-end directed motor dynein are both required for generating efficient pulling forces. We discovered that the Gα proteins and their associated proteins GPR-1/2 and LIN-5 interact in vivo with LIS-1, a component of the dynein complex. Moreover, we uncovered that LIN-5, GPR-1/2 and the Gα proteins promote the presence of the dynein complex at the cell cortex. Our findings suggest a mechanism by which the Gα proteins enable GPR-1/2 and LIN-5 recruitment to the cortex, thus ensuring the presence of cortical dynein. Together with microtubule dynamics, this allows pulling forces to be exerted and proper cell division to be achieved. Because the mechanisms of spindle positioning and asymmetric cell division are conserved across evolution, we expect the underlying mechanism uncovered here to be of broad significance for the generation of cell diversity during development. Moreover, this mechanism could be relevant for other asymmetric cell divisions, such as stem cell divisions, whose dysfunction may lead to the generation of cancer cells.

Specialisation in Europe and asymmetric shocks: potential risks of EMU

Most optimistic views, based on Optimum Currency Areas (OCA) literature, have concluded that the probability of asymmetric shocks to occur at anational level will tend to diminish in the Economic and Monetary Union (EMU)as a result of the intensification of the integration process during the most recent years. Therefore, since Economic Geography Theories predict a higherspecialisation of regions, it is expected that asymmetric shocks will increase.Previous studies have examined to what extent asymmetric shocks have been relevant in the past using, mainly, static measures of asymmetries such as the correlation coefficients between series of shocks previously calculated from astructural VAR model (Bayoumi and Eichengreen, 1992).In this paper, we study the evolution of manufacturing specific asymmetries in Europe from a dynamic point of view (applying the modelproposed by Haldane and Hall, 1991) in order to obtain new evidence about potential risks of EMU.

Time consistent Pareto solutions in common access resource gameswith asymmetric players

In the analysis of equilibrium policies in a di erential game, if agents have different time preference rates, the cooperative (Pareto optimum) solution obtained by applying the Pontryagin's Maximum Principle becomes time inconsistent. In this work we derive a set of dynamic programming equations (in discrete and continuous time) whose solutions are time consistent equilibrium rules for N-player cooperative di erential games in which agents di er in their instantaneous utility functions and also in their discount rates of time preference. The results are applied to the study of a cake-eating problem describing the management of a common property exhaustible natural resource. The extension of the results to a simple common property renewable natural resource model in in nite horizon is also discussed.

Specialisation in Europe and asymmetric shocks: potential risks of EMU

Most optimistic views, based on Optimum Currency Areas (OCA) literature, have concluded that the probability of asymmetric shocks to occur at anational level will tend to diminish in the Economic and Monetary Union (EMU)as a result of the intensification of the integration process during the most recent years. Therefore, since Economic Geography Theories predict a higherspecialisation of regions, it is expected that asymmetric shocks will increase.Previous studies have examined to what extent asymmetric shocks have been relevant in the past using, mainly, static measures of asymmetries such as the correlation coefficients between series of shocks previously calculated from astructural VAR model (Bayoumi and Eichengreen, 1992).In this paper, we study the evolution of manufacturing specific asymmetries in Europe from a dynamic point of view (applying the modelproposed by Haldane and Hall, 1991) in order to obtain new evidence about potential risks of EMU.

Domain growth in binary mixtures at low temperatures

We have studied domain growth during spinodal decomposition at low temperatures. We have performed a numerical integration of the deterministic time-dependent Ginzburg-Landau equation with a variable, concentration-dependent diffusion coefficient. The form of the pair-correlation function and the structure function are independent of temperature but the dynamics is slower at low temperature. A crossover between interfacial diffusion and bulk diffusion mechanisms is observed in the behavior of the characteristic domain size. This effect is explained theoretically in terms of an equation of motion for the interface.

Dynamic structure function in 3-4He mixtures

Relevant features of the dynamic structure function S(q,¿) in 3-4He mixtures at zero temperature are investigated starting from known properties of the ground state. Sum rules are used to fix rigorous constraints to the different contributions to S(q,¿), coming from 3He and 4He elementary excitations, as well as to explore the role of the cross term S(3,4)(q,¿). Both the low-q (phonon-roton 4He excitations and 1p-1h 3He excitations) and high-q (deep-inelastic-scattering) ranges are discussed.

Cavitation in 3He-4He liquid mixtures at low temperatures

Bubble formation in solutions of 3He and 4He is studied within a density-functional approach. In particular, the temperature dependence of the cavitation pressure for different 3He concentrations is calculated at low temperatures and compared to that of pure 4He. The presence of Andreev states lowers the surface tension and, consequently, nucleation barriers are drastically reduced. This fact means that even at low 3He concentrations the cavitation process takes place at higher pressures than the spinodal pressure, which is not the case for pure 4He.

Correlations in hot asymmetric nuclear matter

Bulk and single-particle properties of hot hyperonic matter are studied within the Brueckner-Hartree-Fock approximation extended to finite temperature. The bare interaction in the nucleon sector is the Argonne V18 potential supplemented with an effective three-body force to reproduce the saturating properties of nuclear matter. The modern Nijmegen NSC97e potential is employed for the hyperon-nucleon and hyperon-hyperon interactions. The effect of temperature on the in-medium effective interaction is found to be, in general, very small and the single-particle potentials differ by at most 25% for temperatures in the range from 0 to 60 MeV. The bulk properties of infinite matter of baryons, either nuclear isospin symmetric or a Beta-stable composition that includes a nonzero fraction of hyperons, are obtained. It is found that the presence of hyperons can modify the thermodynamical properties of the system in a non-negligible way.