979 resultados para quantum information theory


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O objetivo final deste estudo é contribuir para a discussão sobre qual a medida em que conceitos semânticos e discursivos estão sintaticamente codificados. Mais especificamente, investiga-se se existe alguma correlação consistente entre alguns aspetos interpretativos e sintáticos de quatro construções clivadas do Português Europeu, e como se deve dar conta teoricamente destas potenciais correlações. As clivadas consideradas são as clivadas canónicas, as pseudoclivadas, as clivadas de é que e as clivadas de SER. Sintaticamente podemos distinguir dois tipos: clivadas bioracionais (canónicas e pseudoclivadas) e clivadas mono-oracionais (clivadas de é que e de SER). Todas as estruturas têm um constituinte clivado focalizado que pode constituir tanto um foco informacional como um foco contrastivo, e uma oração clivada que introduz uma pressuposição existencial. Adicionalmente, o constituinte clivado identifica exaustivamente uma posição vazia na oração clivada. Adota-se a semântica alternativa para o foco (Rooth 1985), segundo a qual o foco entoacional contribui uniformemente um conjunto de alternativas na Forma Lógica. Regras pragmáticas operando neste conjunto dão origem a duas implicaturas que podem ser suspensas: pressuposição existencial e exaustividade. Dado que as clivadas de é que e as de SER têm a mesma interpretação que orações não-clivadas, conclui-se que a sua estrutura sintática particular não contribui para estas propriedades interpretativas. Em contrapartida, as clivadas bioracionais, que são orações copulativas especificacionais, têm uma presuposição existencial e uma interpretação exaustiva que não pode ser suspensa, tal como as orações especificacionais não-clivadas. Argumenta-se que isto se deve ao facto de o constituinte clivado identificar uma variável introduzida por uma descrição definida. Demonstra-se que a oração clivada, uma relativa em posição de complemento de um determinador definido nas clivadas canónicas e uma relativa livre nas pseudoclivadas, tem a mesma denotação que um DP definido, e portanto tem uma pressuposição existencial inerente. A interpretação exaustiva deve-se à relação identificacional entre o constituinte clivado e a descrição definida. Além disso, defende-se que em Português Europeu um traço de foco não desencadeia movimento-A’ para um FocP especializado. Os constituintes focalizados movem-se antes por razões independentes do foco. Isto é confirmado pelo facto de apenas o constituinte clivado das clivadas de é que ter propriedades de movimento A’, os outros parecem estar in situ. Propõe-se que o constituinte clivado das clivadas de é que é um tópico com um traço de foco que se move para um TopP. Esta análise dá conta da existência de restrições discursivas semelhantes para tópicos não focalizados e para o constituinte clivado das clivadas de é que. O traço quantificacional de foco arrastado pela topicalização dá origem a efeitos de intervenção, causando a não-recursividade do foco na periferia esquerda e a sua incompatibilidade com movimento de outros constituintes com traços quantificacionais. A análise prediz as restrições de encaixe observadas para as clivadas de é que. Finalmente, desenvolve-se uma análise sintática das clivadas de SER que aproxima estas estruturas das estruturas com partículas de foco. Propõe-se que a cópula é um operador sensível ao foco que é merged juntamente com o constituinte clivado. As restrições distribucionais da cópula devem-se a requisitos selecionais de núcleos.

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We study markets where the characteristics or decisions of certain agents are relevant but not known to their trading partners. Assuming exclusive transactions, the environment is described as a continuum economy with indivisible commodities. We characterize incentive efficient allocations as solutions to linear programming problems and appeal to duality theory to demonstrate the generic existence of external effects in these markets. Because under certain conditions such effects may generate non-convexities, randomization emerges as a theoretic possibility. In characterizing market equilibria we show that, consistently with the personalized nature of transactions, prices are generally non-linear in the underlying consumption. On the other hand, external effects may have critical implications for market efficiency. With adverse selection, in fact, cross-subsidization across agents with different private information may be necessary for optimality, and so, the market need not even achieve an incentive efficient allocation. In contrast, for the case of a single commodity, we find that when informational asymmetries arise after the trading period (e.g. moral hazard; ex post hidden types) external effects are fully internalized at a market equilibrium.

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Cette thèse examine la circulation et l'intégration des informations scientifiques dans la pensée quotidienne d'après la théorie des représentations sociales (TRS). En tant qu'alternative aux approches traditionnelles de la communication de la science, les transformations survenant entre le discours scientifique et le discours de sens commun sont considérées comme adaptatives. Deux études sur la circulation des informations dans les media (études 1 et 2) montrent des variations dans les thèmes de discours exposés aux profanes, et parmi les discours de ceux-ci, en fonction de différentes sources. Ensuite, le processus d'ancrage dans le positionnement préalable envers la science est étudié, pour l'explication qu'il fournit de la réception et de la transmission d'informations scientifiques dans le sens commun. Les effets d'ancrage dans les attitudes et croyances préexistants sont reportés dans différents contextes de circulation des informations scientifiques (études 3 à 7), incluant des études de type corrélationnel, experimental et de terrain. Globalement, cette thèse procure des arguments en faveur de la pertinence de la TRS pour la recherche sur la communication de la science, et suggère des développements théoriques et méthodologiques pour ces deux domaines de recherche. Drawing on the social representations theory (SRT), this thesis examines the circulation and integration of scientific information into everyday thinking. As an alternative to the traditional approaches of science communication, it considers transformations between scientific and common-sense discourses as adaptive. Two studies, focused on the spreading of information into the media (Studies 1 and 2), show variations in the themes of discourses introduced to laypersons and in the themes among laypersons' discourses, according to different sources. Anchoring in prior positioning toward science is then studied for the explanation it provides on the reception and transmission of scientific information into common sense. Anchoring effects in prior attitudes and beliefs are reported in different contexts of circulation of scientific information (Studies 3 to 7) by using results from correlational, field, and experimental studies. Overall, this thesis provides arguments for the relevance of SRT in science communication research and suggests theoretical and methodological developments for both domains of research.

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We propose an elementary theory of wars fought by fully rational contenders. Two parties play a Markov game that combines stages of bargaining with stages where one side has the ability to impose surrender on the other. Under uncertainty and incomplete information, in the unique equilibrium of the game, long confrontations occur: war arises when reality disappoints initial (rational) optimism, and it persist longer when both agents are optimists but reality proves both wrong. Bargaining proposals that are rejected initially might eventually be accepted after several periods of confrontation. We provide an explicit computation of the equilibrium, evaluating the probability of war, and its expected losses as a function of i) the costs of confrontation, ii) the asymmetry of the split imposed under surrender, and iii) the strengths of contenders at attack and defense. Changes in these parameters display non-monotonic effects.

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Adverse selection may thwart trade between an informed seller, who knows the probability p that an item of antiquity is genuine, and an uninformed buyer, who does not know p. The buyer might not be wholly uninformed, however. Suppose he can perform a simple inspection, a test of his own: the probability that an item passes the test is g if the item is genuine, but only f < g if it is fake. Given that the buyer is no expert, his test may have little power: f may be close to g. Unfortunately, without much power, the buyer's test will not resolve the difficulty of adverse selection; gains from trade may remain unexploited. But now consider a "store", where the seller groups a number of items, perhaps all with the same quality, the same probability p of being genuine. (We show that in equilibrium the seller will choose to group items in this manner.) Now the buyer can conduct his test across a large sample, perhaps all, of a group of items in the seller's store. He can thereby assess the overall quality of these items; he can invert the aggregate of his test results to uncover the underlying p; he can form a "prior". There is thus no longer asymmetric information between seller and buyer: gains from trade can be exploited. This is our theory of retailing: by grouping items together - setting up a store - a seller is able to supply buyers with priors, as well as the items themselves. We show that the weaker the power of the buyer�s test (the closer f is to g), the greater the seller�s profit. So the seller has no incentive to assist the buyer � e.g., by performing her own tests on the items, or by cleaning them to reveal more about their true age. The paper ends with an analysis of which sellers should specialise in which qualities. We show that quality will be low in busy locations and high in expensive locations.

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Game theory describes and analyzes strategic interaction. It is usually distinguished between static games, which are strategic situations in which the players choose only once as well as simultaneously, and dynamic games, which are strategic situations involving sequential choices. In addition, dynamic games can be further classified according to perfect and imperfect information. Indeed, a dynamic game is said to exhibit perfect information, whenever at any point of the game every player has full informational access to all choices that have been conducted so far. However, in the case of imperfect information some players are not fully informed about some choices. Game-theoretic analysis proceeds in two steps. Firstly, games are modelled by so-called form structures which extract and formalize the significant parts of the underlying strategic interaction. The basic and most commonly used models of games are the normal form, which rather sparsely describes a game merely in terms of the players' strategy sets and utilities, and the extensive form, which models a game in a more detailed way as a tree. In fact, it is standard to formalize static games with the normal form and dynamic games with the extensive form. Secondly, solution concepts are developed to solve models of games in the sense of identifying the choices that should be taken by rational players. Indeed, the ultimate objective of the classical approach to game theory, which is of normative character, is the development of a solution concept that is capable of identifying a unique choice for every player in an arbitrary game. However, given the large variety of games, it is not at all certain whether it is possible to device a solution concept with such universal capability. Alternatively, interactive epistemology provides an epistemic approach to game theory of descriptive character. This rather recent discipline analyzes the relation between knowledge, belief and choice of game-playing agents in an epistemic framework. The description of the players' choices in a given game relative to various epistemic assumptions constitutes the fundamental problem addressed by an epistemic approach to game theory. In a general sense, the objective of interactive epistemology consists in characterizing existing game-theoretic solution concepts in terms of epistemic assumptions as well as in proposing novel solution concepts by studying the game-theoretic implications of refined or new epistemic hypotheses. Intuitively, an epistemic model of a game can be interpreted as representing the reasoning of the players. Indeed, before making a decision in a game, the players reason about the game and their respective opponents, given their knowledge and beliefs. Precisely these epistemic mental states on which players base their decisions are explicitly expressible in an epistemic framework. In this PhD thesis, we consider an epistemic approach to game theory from a foundational point of view. In Chapter 1, basic game-theoretic notions as well as Aumann's epistemic framework for games are expounded and illustrated. Also, Aumann's sufficient conditions for backward induction are presented and his conceptual views discussed. In Chapter 2, Aumann's interactive epistemology is conceptually analyzed. In Chapter 3, which is based on joint work with Conrad Heilmann, a three-stage account for dynamic games is introduced and a type-based epistemic model is extended with a notion of agent connectedness. Then, sufficient conditions for backward induction are derived. In Chapter 4, which is based on joint work with Jérémie Cabessa, a topological approach to interactive epistemology is initiated. In particular, the epistemic-topological operator limit knowledge is defined and some implications for games considered. In Chapter 5, which is based on joint work with Jérémie Cabessa and Andrés Perea, Aumann's impossibility theorem on agreeing to disagree is revisited and weakened in the sense that possible contexts are provided in which agents can indeed agree to disagree.

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The dissertation investigates some relevant metaphysical issues arising in the context of spacetime theories. In particular, the inquiry focuses on general relativity and canonical quantum gravity. A formal definition of spacetime theory is proposed and, against this framework, an analysis of the notions of general covariance, symmetry and background independence is performed. It is argued that many conceptual issues in general relativity and canonical quantum gravity derive from putting excessive emphasis on general covariance as an ontological prin-ciple. An original metaphysical position grounded in scientific essential- ism and causal realism (weak essentialism) is developed and defended. It is argued that, in the context of general relativity, weak essentialism supports spacetime substantivalism. It is also shown that weak essentialism escapes arguments from metaphysical underdetermination by positing a particular kind of causation, dubbed geometric. The proposed interpretive framework is then applied to Bohmian mechanics, pointing out that weak essentialism nicely fits into this theory. In the end, a possible Bohmian implementation of loop quantum gravity is considered, and such a Bohmian approach is interpreted in a geometric causal fashion. Under this interpretation, Bohmian loop quantum gravity straightforwardly commits us to an ontology of elementary extensions of space whose evolution is described by a non-local law. The causal mechanism underlying this evolution clarifies many conceptual issues related to the emergence of classical spacetime from the quantum regime. Although there is as yet no fully worked out physical theory of quantum gravity, it is argued that the proposed approach sets up a standard that proposals for a serious ontology in this field should meet.

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We study the interaction between nonprice public rationing and prices in the private market. Under a limited budget, the public supplier uses a rationing policy. A private firm may supply the good to those consumers who are rationed by the public system. Consumers have different amounts of wealth, and costs of providing the good to them vary. We consider two regimes. First, the public supplier observes consumers' wealth information; second, the public supplier observes both wealth and cost information. The public supplier chooses a rationing policy, and, simultaneously, the private firm, observing only cost but not wealth information, chooses a pricing policy. In the first regime, there is a continuum of equilibria. The Pareto dominant equilibrium is a means-test equilibrium: poor consumers are supplied while rich consumers are rationed. Prices in the private market increase with the budget. In the second regime, there is a unique equilibrium. This exhibits a cost-effectiveness rationing rule; consumers are supplied if and only if their costbenefit ratios are low. Prices in the private market do not change with the budget. Equilibrium consumer utility is higher in the cost-effectiveness equilibrium than the means-test equilibrium [Authors]

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Es presenta un nou algorisme per a la diagonalització de matrius amb diagonal dominant. Es mostra la seva eficàcia en el tractament de matrius no simètriques, amb elements definits sobre el cos complex i, fins i tot, de grans dimensions. Es posa de manifest la senzillesa del mètode així com la facilitat d'implementació en forma de codi de programació. Es comentenels seus avantatges i característiques limitants, així com algunes de les millores que es poden implementar. Finalment, es mostren alguns exemples numèrics

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Es descriu l'aproximació de Capes Atòmiques dins de la teoria de la Semblança Molecular Quàntica. Partint només de dades teòriques, s'ha trobat una relació entre estructura molecular i activitat biològica per a diversos conjunts de molècules. Es descriuen els aspectes teòrics de la Semblança Molecular Quàntica i alguns exemples d'aplicació

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This document contains a report and summary of the field research activities in a rural community of rice farmers in Kampot province, Cambodia in 2011, which I conducted within the context of my PhD research at ICTA-UAB (Institute of Environmental Science and Technology, Autonomous University of Barcelona, Spain). The purpose of the field research was to gather data for a MuSIASEM analysis (Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism) at the village and household level, in order to analyze the multidimensional challenges that small farmers may face nowadays within the context of global rural change and declining access to land. While the literature on MuSIASEM offers a great variety of theoretical explanations and practical applications, there is little information available for students regarding the practical steps required for doing a MuSIASEM analysis at the local level. Within this context, this report offers not only a documentation of the field research design and data collection methods, but further provides a general overview on some organizational and preparative aspects, including some personal reflections, that one may face when preparing and conducting field research for MuSIASEM analysis. In summary, this document thus serves three objectives: (i) to assure methodological transparency for the future work, based on the collected data during field research, (ii) to share my personal experience on the preparative and practical steps required for field research and data collection for a MuSIASEM analysis at the local level, and (iii) to make available for the further interested reader some more detailed background information on the case study village.

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The radiation distribution function used by Domínguez and Jou [Phys. Rev. E 51, 158 (1995)] has been recently modified by Domínguez-Cascante and Faraudo [Phys. Rev. E 54, 6933 (1996)]. However, in these studies neither distribution was written in terms of directly measurable quantities. Here a solution to this problem is presented, and we also propose an experiment that may make it possible to determine the distribution function of nonequilibrium radiation experimentally. The results derived do not depend on a specific distribution function for the matter content of the system

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A new practical method to generate a subspace of active coordinates for quantum dynamics calculations is presented. These reduced coordinates are obtained as the normal modes of an analytical quadratic representation of the energy difference between excited and ground states within the complete active space self-consistent field method. At the Franck-Condon point, the largest negative eigenvalues of this Hessian correspond to the photoactive modes: those that reduce the energy difference and lead to the conical intersection; eigenvalues close to 0 correspond to bath modes, while modes with large positive eigenvalues are photoinactive vibrations, which increase the energy difference. The efficacy of quantum dynamics run in the subspace of the photoactive modes is illustrated with the photochemistry of benzene, where theoretical simulations are designed to assist optimal control experiments

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Quantum molecular similarity (QMS) techniques are used to assess the response of the electron density of various small molecules to application of a static, uniform electric field. Likewise, QMS is used to analyze the changes in electron density generated by the process of floating a basis set. The results obtained show an interrelation between the floating process, the optimum geometry, and the presence of an external field. Cases involving the Le Chatelier principle are discussed, and an insight on the changes of bond critical point properties, self-similarity values and density differences is performed