Agreements with overlapping coalitions

Dans certaines circonstances, des actions de groupes sont plus performantes que des actions individuelles. Dans ces situations, il est préférable de former des coalitions. Ces coalitions peuvent être disjointes ou imbriquées. La littérature économique met un fort accent sur la modélisation des accords où les coalitions d’agents économiques sont des ensembles disjoints. Cependant on observe dans la vie de tous les jours que les coalitions politiques, environnementales, de libre-échange et d’assurance informelles sont la plupart du temps imbriquées. Aussi, devient-il impératif de comprendre le fonctionnement économique des coalitions imbriquées. Ma thèse développe un cadre d’analyse qui permet de comprendre la formation et la performance des coalitions même si elles sont imbriquées. Dans le premier chapitre je développe un jeu de négociation qui permet la formation de coalitions imbriquées. Je montre que ce jeu admet un équilibre et je développe un algorithme pour calculer les allocations d’équilibre pour les jeux symétriques. Je montre que toute structure de réseau peut se décomposer de manière unique en une structure de coalitions imbriquées. Sous certaines conditions, je montre que cette structure correspond à une structure d’équilibre d’un jeu sous-jacent. Dans le deuxième chapitre j’introduis une nouvelle notion de noyau dans le cas où les coalitions imbriquées sont permises. Je montre que cette notion de noyau est une généralisation naturelle de la notion de noyau de structure de coalitions. Je vais plus loin en introduisant des agents plus raffinés. J’obtiens alors le noyau de structure de coalitions imbriquées que je montre être un affinement de la première notion. Dans la suite de la thèse, j’applique les théories développées dans les deux premiers chapitres à des cas concrets. Le troisième chapitre est une application de la relation biunivoque établie dans le premier chapitre entre la formation des coalitions et la formation de réseaux. Je propose une modélisation réaliste et effective des assurances informelles. J’introduis ainsi dans la littérature économique sur les assurances informelles, quatre innovations majeures : une fusion entre l’approche par les groupes et l’approche par les réseaux sociaux, la possibilité d’avoir des organisations imbriquées d’assurance informelle, un schéma de punition endogène et enfin les externalités. Je caractérise les accords d’assurances informelles stables et j’isole les conditions qui poussent les agents à dévier. Il est admis dans la littérature que seuls les individus ayant un revenu élevé peuvent se permettre de violer les accords d’assurances informelles. Je donne ici les conditions dans lesquelles cette hypothèse tient. Cependant, je montre aussi qu’il est possible de violer cette hypothèse sous d’autres conditions réalistes. Finalement je dérive des résultats de statiques comparées sous deux normes de partage différents. Dans le quatrième et dernier chapitre, je propose un modèle d’assurance informelle où les groupes homogènes sont construits sur la base de relations de confiance préexistantes. Ces groupes sont imbriqués et représentent des ensembles de partage de risque. Cette approche est plus générale que les approches traditionnelles de groupe ou de réseau. Je caractérise les accords stables sans faire d’hypothèses sur le taux d’escompte. J’identifie les caractéristiques des réseaux stables qui correspondent aux taux d’escomptes les plus faibles. Bien que l’objectif des assurances informelles soit de lisser la consommation, je montre que des effets externes liés notamment à la valorisation des liens interpersonnels renforcent la stabilité. Je développe un algorithme à pas finis qui égalise la consommation pour tous les individus liés. Le fait que le nombre de pas soit fini (contrairement aux algorithmes à pas infinis existants) fait que mon algorithme peut inspirer de manière réaliste des politiques économiques. Enfin, je donne des résultats de statique comparée pour certaines valeurs exogènes du modèle.

Autoreporte de la calidad de vida en niños y adolescentes colombianos: Estudio FUPRECOL

RESUMEN Introducción: El EQ-5D-Y proxy es un cuestionario genérico, de fácil comprensión y aplicación, que evalúa distintas dimensiones de la salud percibida. El objetivo del siguiente estudio fue describir por autoreporte la calidad de vida relacionada con la salud (CVRS) en una población escolar de Bogotá, Colombia, pertenecientes al estudio FUPRECOL. Métodos: Estudio descriptivo y transversal, realizado en 3.245 niños y 3.354 adolescentes, entre 9 y 17.9 años de edad, de 24 instituciones educativas oficiales de Bogotá, Colombia. Se aplicó de manera auto-administrada la versión validada al castellano por Olivares et al. (2009) del instrumento de CVRS infantil EQ-5D-Y proxy. Se analizaron los datos por medidas de tendencia central y se realizó una comparación de los observados en Colombia con estudios internacionales. Resultados: De la población evaluada, el 58,3% (n=3.848), fueron mujeres. En general, se observa puntuaciones elevadas en la CVRS en niños y adolescentes de ambos sexos. Al comparar por género, las dimensiones del EQ-5D-Y proxy “sentirse triste/preocupado o infeliz” y “tener dolor/malestar”, presentaron la mayor frecuencia de repuesta en el grupo de las mujeres. Al comparar los resultados de este estudio, por grupos de edad, con trabajos internacionales de niños y adolescentes, se observa que las puntuaciones del EQ-5D-Y proxy fueron superiores a los reportados en Suráfrica, Alemania e Italia. Conclusión: Se presentan valores de la CVRS según edad y sexo que podrán ser usados en la evaluación de la salud percibida en el ámbito escolar. Se hace necesario evaluar las propiedades psicométricas del EQ-5D-Y proxy en población Colombiana.

The convenient synthesis of a liquid-crystalline polyacrylate with a tetramethylene spacer

A protecting group approach to the synthesis of a liquid crystalline polyacrylate containing a tetramethylene spacer unit is described. This approach prevents the formation of side products obtained when a more direct synthetic pathway is used. The resulting material shows behaviour typical of a nematic liquid crystal polymer.

Limitations of small x resummation methods from F2data

We discuss several methods of calculating the DIS structure functions F2(x,Q2) based on BFKL-type small x resummations. Taking into account new HERA data ranging down to small xand low Q2, the pure leading order BFKL-based approach is excluded. Other methods based on high energy factorization are closer to conventional renormalization group equations. Despite several difficulties and ambiguities in combining the renormalization group equations with small x resummed terms, we find that a fit to the current data is hardly feasible, since the data in the low Q2 region are not as steep as the BFKL formalism predicts. Thus we conclude that deviations from the (successful) renormalization group approach towards summing up logarithms in 1/x are disfavoured by experiment.

Modelo de ashkin-teller de três cores na rede ponte de wheatstone

In this work we study the phase transitions of the ferromagnetic three-color Ashkin-Teller Model in the hierarquical lattice generated by the Wheatstone bridge using real space renormalization group approach. With such technique we obtain the phase diagram and its critical points with respective critical exponents v. This model presents four phases: ferromagnetic, paramagnetic and two intermediates. Nine critical points were found, three of which are of Ising model type, three are of four states Potts model type, one is of eight states Potts model type and the last two which do not correspond to any Potts model with integer number of states. iv

A educação não-formal como campo de estágio: contribuições na formação inicial do arte/educador

Pós-graduação em Artes - IA

Cálculo de grupos de homotopia dos grupos clássicos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Sequências espectrais e aplicações aos cálculos de cohomologias de espaços fibrados

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Abordagem em grupo na atenção primária: o caso do Grupo do colesterol de Centro de saúde Escola de Botucatu

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comparative Analysis of Approaches for Assessing Energy Intake Underreporting by Female Bariatric Surgery Candidates

Objective: To test six variations in the Goldberg equation for evaluating the underreporting of energy intake (EI) among obese women on the waiting list for bariatric surgery, considering variations in resting metabolic rate (RMR), physical activity, and food intake levels in group and individual approaches.Methods: One hundred obese women aged 20 to 45years (33.3 6.08) recruited from a bariatric surgery waiting list participated in the study. Underreporting assessment was based on the difference between reported energy intake, indirect calorimetry measurements and RMR (rEI:RMR), which is compatible with the predicted physical activity level (PAL). Six approaches were used for defining the cutoff points. The approaches took into account variances in the components of the rEI:RMR = PAL equation as a function of the assumed PAL, sample size (n), and measured or estimated RMR.Results: The underreporting percentage varied from 55% to 97%, depending on the approach used for generating the cutoff points. The ratio rEI:RMR and estimated PAL of the sample were significantly different (p = 0.001). Sixty-one percent of the women reported an EI lower than their RMR. The PAL variable significantly affected the cutoff point, leading to different proportions of underreporting. The RMR measured or estimated in the equation did not result in differences in the proportion of underreporting. The individual approach was less sensitive than the group approach.Conclusion: RMR did not interfere in underreporting estimates. However, PAL variations were responsible for significant differences in cutoff point. Thus, PAL should be considered when estimating underreporting, and even though the individual approach is less sensitive than the group approach, it may be a useful tool for clinical practice.

Reply to 'Lifshitz-point critical behaviour to O(εL 2)'

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Orthogonality relations and supercharacter formulas of U(m vertical bar n) representations

In this paper we obtain the orthogonality relations for the supergroup U(m|n), which are remarkably different from the ones for the U(N) case. We extend our results for ordinary representations, obtained some time ago, to the case of complex conjugated and mixed representations. Our results are expressed in terms of the Young tableaux notation for irreducible representations. We use the supersymmetric Harish-Chandra-Itzykson-Zuber integral and the character expansion technique as mathematical tools for deriving these relations. As a byproduct we also obtain closed expressions for the supercharacters and dimensions of some particular irreducible U(m|n) representations. A new way of labeling the U(m|n) irreducible representations in terms of m + n numbers is proposed. Finally, as a corollary of our results, new identities among the dimensions of the irreducible representations of the unitary group U(N) are presented. © 1997 American Institute of Physics.

Dissipation effects in random transverse-field Ising chains

We study the effects of Ohmic, super-Ohmic, and sub-Ohmic dissipation on the zero-temperature quantum phase transition in the random transverse-field Ising chain by means of an (asymptotically exact) analytical strong-disorder renormalization-group approach. We find that Ohmic damping destabilizes the infinite-randomness critical point and the associated quantum Griffiths singularities of the dissipationless system. The quantum dynamics of large magnetic clusters freezes completely, which destroys the sharp phase transition by smearing. The effects of sub-Ohmic dissipation are similar and also lead to a smeared transition. In contrast, super-Ohmic damping is an irrelevant perturbation; the critical behavior is thus identical to that of the dissipationless system. We discuss the resulting phase diagrams, the behavior of various observables, and the implications to higher dimensions and experiments.

Black hole formation with an interacting vacuum energy density

We discuss the gravitational collapse of a spherically symmetric massive core of a star in which the fluid component is interacting with a growing vacuum energy density. The influence of the variable vacuum in the collapsing core is quantified by a phenomenological beta parameter as predicted by dimensional arguments and the renormalization group approach. For all reasonable values of this free parameter, we find that the vacuum energy density increases the collapsing time, but it cannot prevent the formation of a singular point. However, the nature of the singularity depends on the value of beta. In the radiation case, a trapped surface is formed for beta <= 1/2, whereas for beta >= 1/2, a naked singularity is developed. In general, the critical value is beta = 1-2/3(1 + omega) where omega is the parameter describing the equation of state of the fluid component.

Toeplitz operators on finite and infinite dimensional spaces with associated psi *-Fréchet algebras

The present thesis is a contribution to the multi-variable theory of Bergman and Hardy Toeplitz operators on spaces of holomorphic functions over finite and infinite dimensional domains. In particular, we focus on certain spectral invariant Frechet operator algebras F closely related to the local symbol behavior of Toeplitz operators in F. We summarize results due to B. Gramsch et.al. on the construction of Psi_0- and Psi^*-algebras in operator algebras and corresponding scales of generalized Sobolev spaces using commutator methods, generalized Laplacians and strongly continuous group actions. In the case of the Segal-Bargmann space H^2(C^n,m) of Gaussian square integrable entire functions on C^n we determine a class of vector-fields Y(C^n) supported in complex cones K. Further, we require that for any finite subset V of Y(C^n) the Toeplitz projection P is a smooth element in the Psi_0-algebra constructed by commutator methods with respect to V. As a result we obtain Psi_0- and Psi^*-operator algebras F localized in cones K. It is an immediate consequence that F contains all Toeplitz operators T_f with a symbol f of certain regularity in an open neighborhood of K. There is a natural unitary group action on H^2(C^n,m) which is induced by weighted shifts and unitary groups on C^n. We examine the corresponding Psi^*-algebra A of smooth elements in Toeplitz-C^*-algebras. Among other results sufficient conditions on the symbol f for T_f to belong to A are given in terms of estimates on its Berezin-transform. Local aspects of the Szegö projection P_s on the Heisenbeg group and the corresponding Toeplitz operators T_f with symbol f are studied. In this connection we apply a result due to Nagel and Stein which states that for any strictly pseudo-convex domain U the projection P_s is a pseudodifferential operator of exotic type (1/2, 1/2). The second part of this thesis is devoted to the infinite dimensional theory of Bergman and Hardy spaces and the corresponding Toeplitz operators. We give a new proof of a result observed by Boland and Waelbroeck. Namely, that the space of all holomorphic functions H(U) on an open subset U of a DFN-space (dual Frechet nuclear space) is a FN-space (Frechet nuclear space) equipped with the compact open topology. Using the nuclearity of H(U) we obtain Cauchy-Weil-type integral formulas for closed subalgebras A in H_b(U), the space of all bounded holomorphic functions on U, where A separates points. Further, we prove the existence of Hardy spaces of holomorphic functions on U corresponding to the abstract Shilov boundary S_A of A and with respect to a suitable boundary measure on S_A. Finally, for a domain U in a DFN-space or a polish spaces we consider the symmetrizations m_s of measures m on U by suitable representations of a group G in the group of homeomorphisms on U. In particular,in the case where m leads to Bergman spaces of holomorphic functions on U, the group G is compact and the representation is continuous we show that m_s defines a Bergman space of holomorphic functions on U as well. This leads to unitary group representations of G on L^p- and Bergman spaces inducing operator algebras of smooth elements related to the symmetries of U.