Social Choice: Recent Developments

In the past quarter century, there has been a dramatic shift of focus in social choice theory, with structured sets of alternatives and restricted domains of the sort encountered in economic problems coming to the fore. This article provides an overview of some of the recent contributions to four topics in normative social choice theory in which economic modelling has played a prominent role: Arrovian social choice theory on economic domains, variable-population social choice, strategy-proof social choice, and axiomatic models of resource allocation.

Oligarchies in Spatial Environments

In spatial environments we consider social welfare functions satisfying Arrow’s requirements, i.e. weak Pareto and independence of irrelevant alternatives. Individual preferences measure distances between alternatives according to the Lp-norm (for a fixed p => 1). When the policy space is multi-dimensional and the set of alternatives has a non-empty interior and it is compact and convex, any quasi-transitive welfare function must be oligarchic. As a corollary we obtain that for transitive welfare functions weak Pareto, independence of irrelevant alternatives, and non-dictatorship are inconsistent if the set of alternatives has a non-empty interior and it is compact and convex.

Multi-Profile Intergenerational Social Choice

Ferejohn and Page transplanted a stationarity axiom from Koopmans’ theory of impatience into Arrow’s social choice theory with an infinite horizon and showed that the Arrow axioms and stationarity lead to a dictatorship by the first generation. We prove that the negative implications of their stationarity axiom are more far-reaching: there is no Arrow social welfare function satisfying their stationarity axiom. We propose a more suitable stationarity axiom, and show that an Arrow social welfare function satisfies this modified version if and only if it is a lexicographic dictatorship where the generations are taken into consideration in chronological order.

Multi-Profile Intertemporal Social Choice

We provide a brief survey of some literature on intertemporal social choice theory in a multi-profile setting. As is well-known, Arrow’s impossibility result hinges on the assumption that the population is finite. For infinite populations, there exist nondictatorial social welfare functions satisfying Arrow’s axioms and they can be described by their corresponding collections of decisive coalitions. We review contributions that explore whether this possibility in the infinite-population context allows for a richer class of social welfare functions in an intergenerational model. Different notions of stationarity formulated for individual and for social preferences are examined. Journal of Economic Literature Classification No.: D71.

La flèche du temps : analyse philosophique d'une métaphore scientifique

Le problème de la direction du temps est un problème classique autant en physique qu’en philosophie. Quoiqu’il existe plusieurs façons de s’interroger sur ce problème, l’approche thermodynamique est la plus fréquemment utilisée. Cette approche consiste à considérer la flèche du temps thermodynamique comme la flèche fondamentale de laquelle les autres flèches ne sont que des manifestations. Ce mémoire vise à fournir une analyse philosophique de cette approche. Pour ce faire, nous esquisserons la problématique générale, nous exposerons les différentes approches et théories alternatives visant à résoudre ce problème et nous présenterons la thèse forte soutenant l’approche thermodynamique. Ensuite, nous évaluerons la pertinence du recours à la mécanique statistique et à la cosmologie visant à remédier aux déficiences de cette même approche. Enfin, nous analyserons en quoi cette approche, et plus particulièrement la notion d’entropie, est en mesure de fournir un cadre conceptuel pour la résolution du problème de la flèche du temps.

Iris Murdoch

This is an analysis of Iris Murdoch's plays, including The Italian Girl, The Severed Head, The Black Prince, The Three Arrows and The Servants and the Snow. It also assesses Murdoch's significance for theatre in the early 1960s and 70s, as Women's Theatre was beginning to make its mark.

The bound quiver of a split extension

In this paper, we give a sufficient (which is also necessary under a compatibility hypothesis) condition on a set of arrows in the quiver of an algebra A so that A is a split extension of A/M, where M is the ideal of A generated by the classes of these arrows. We also compare the notion of split extension with that of semiconvex extension of algebras.

Solving the non-convexity problem in some shopping-time and human-capital models

Several works in the shopping-time and in the human-capital literature, due to the nonconcavity of the underlying Hamiltonian, use Örst-order conditions in dynamic optimization to characterize necessity, but not su¢ ciency, in intertemporal problems. In this work I choose one paper in each one of these two areas and show that optimality can be characterized by means of a simple aplication of Arrowís (1968) su¢ ciency theorem.

Evaluation of the Cartographic Communication Performance of a Route Guidance and Navigation System

This study evaluates the influence of different cartographic representations of in-car navigation systems on visual demand, subjective preference, and navigational error. It takes into account the type and complexity of the representation, maneuvering complexity, road layout, and driver gender. A group of 28 drivers (14 male and 14 female) participated in this experiment which was performed in a low-cost driving simulator. The tests were performed on a limited number of instances for each type of representation, and their purpose was to carry out a preliminary assessment and provide future avenues for further studies. Data collected for the visual demand study were analyzed using non-parametric statistical analyses. Results confirmed previous research that showed that different levels of design complexity significantly influence visual demand. Non-grid-like road networks, for example, influence significantly visual demand and navigational error. An analysis of simple maneuvers on a grid-like road network showed that static and blinking arrows did not present significant differences. From the set of representations analyzed to assess visual demand, both arrows were equally efficient. From a gender perspective, women seem to took at the display more than men, but this factor was not significant. With respect to subjective preferences, drivers prefer representations with mimetic landmarks when they perform straight-ahead tasks. For maneuvering tasks, landmarks in a perspective model created higher visual demands.

Nutritional stress enhances cell viability of odontoblast-like cells subjected to low level laser irradiation

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

Fisheries and fishing effort at the Indigenous Reserves Ashaninka/Kaxinawá, river Breu, Brazil/Peru

Este artigo tem o objetivo de descrever a pesca de subsistência das populações tradicionais de uma aldeia Ashaninka e duas Kaxinawá vivendo à beira do rio Breu. Inicialmente, foram treinados monitores para preencher fichas de coleta de dados das pescarias nas aldeias durante um ciclo anual (agosto/1995 agosto/1996). A partir desses dados realizaram-se os inventários das espécies de peixes capturadas e dos ambientes pesqueiros. A análise dos dados foi efetuada por meio de estatística descritiva e exploratória. Os resultados obtidos foram os seguintes: i) os ambientes mais procurados pelos índios foram os poços; ii) as espécies mais capturadas os mandis (35%, Pimelodidae), os bodes ou cascudos (Loricariidae), com destaque para o bode praiano (25%, Hypostomus sp.), o curimatã (9%, Prochilodus sp.) e os saburus (8%, Curimatidae), entre outros; iii) constatou-se que os arreios ou apetrechos de pesca que mais capturam peixes são o tingui (veneno), a tarrafa e o arco/flecha, respectivamente; iv) durante o verão a atividade de pesca é mais intensa; v) as medidas de esforço de pesca e os fatores associados que foram estatisticamente significativos nas predições das capturas na Reserva Indígena foram: f1 = o (número de pescadores), f2 = o (número de pescadores*tempo total das pescarias) e f3 = o [(número de pescadores*tempo total das pescarias)-(o tempo de deslocamento)] e os fatores aldeias e arreios; vi) apesar da maioria das pescarias serem realizadas a pé até os pesqueiros, as capturas são maiores quando a locomoção se dá através de canoa a remo; e vii) os pescadores mais ativos nas pescarias na Reserva Indígena foram os Kaxinawá.

Seleção de informações de guia de rota para a concepção de sistemas de navegação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo experimental de vigas de alvenaria estrutural sujeitas à flexão

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência da mesa na resistência ao cisalhamento de lajes nervuradas unidirecionais de concreto armado

A resistência ao cisalhamento de lajes nervuradas unidirecionais de concreto armado sem armadura transversal em suas nervuras é avaliada através de seu comportamento estrutural ao cisalhamento. Para quantificar a participação da altura da mesa e da mesa colaborante na resistência característica ao cisalhamento, foram confeccionados 8 painéis de lajes nervuradas unidirecionais de concreto armado com variações da altura das mesas, visando avaliar as recomendações das normas NBR 6118 (2007), ACI 318 (2011) e EUROCODE 2 (2002) no que se refere ao desempenho das lajes nervuradas unidirecionais de concreto armado ao cisalhamento. As lajes, simplesmente apoiadas nas bordas, apresentaram-se em dois grupos, buscando abranger os limites prescritos pela norma brasileira: o primeiro com 4 lajes de (2000 x 1300) mm² com distância entre os eixos de nervuras de 610 mm e o segundo com 4 lajes de (2000 x 2000) mm² com distância entre eixos de nervuras de 960 mm, sendo que houve uma variação da altura da mesa de 30, 50, 80 e 100 mm. A armadura de flexão foi mantida constante em todos os casos e a armadura de cisalhamento foi suprimida, para que todas as lajes tivessem rupturas por cisalhamento. As lajes apresentaram aumento da resistência com o aumento da altura da mesa, indicado pelo considerável ganho de contribuição do concreto na resistência ao cisalhamento, bem como a grande deformação das armaduras longitudinais e de distribuição, e pelos elevados valores das flechas. Portanto, no cálculo de resistência ao cisalhamento de lajes nervuradas, poderia ser repensada a falta da utilização da altura da mesa como variável, visto que sua contribuição à resistência ao cisalhamento é real.

Supersymmetric Dark Matter : aspects of sfermion coannihilations

There is very strong evidence that ordinary matter in the Universe is outweighed by almost ten times as much so-called dark matter. Dark matter does neither emit nor absorb light and we do not know what it is. One of the theoretically favoured candidates is a so-called neutralino from the supersymmetric extension of the Standard Model of particle physics. A theoretical calculation of the expected cosmic neutralino density must include the so-called coannihilations. Coannihilations are particle processes in the early Universe with any two supersymmetric particles in the initial state and any two Standard Model particles in the final state. In this thesis we discuss the importance of these processes for the calculation of the relic density. We will go through some details in the calculation of coannihilations with one or two so-called sfermions in the initial state. This includes a discussion of Feynman diagrams with clashing arrows, a calculation of colour factors and a discussion of ghosts in non-Abelian field theory. Supersymmetric models contain a large number of free parameters on which the masses and couplings depend. The requirement, that the predicted density of cosmic neutralinos must agree with the density observed for the unknown dark matter, will constrain the parameters. Other constraints come from experiments which are not related to cosmology. For instance, the supersymmetric loop contribution to the rare b -> sγ decay should agree with the measured branching fraction. The principles of the calculation of the rare decay are discussed in this thesis. Also on-going and planned searches for cosmic neutralinos can constrain the parameters. In one of the accompanying papers in the thesis we compare the detection prospects for several current and future searches for neutralino dark matter.