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Órbitas de Lyapunov no problema de n vórtices no plano e na esferaCosta Carvalho, Adecarlos 31 January 2012 (has links)
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Previous issue date: 2012 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Neste trabalho tratamos da existência de orbitas periodicas numa vizinhanca de equilibrios relativos
no problema de n vortices no plano e na esfera. Mais especificamente, no plano, o equilibrio
relativo consiste de n vortices unitarios nos vertices de um poligono regular inscrito numa circunferência centrada na origem com e sem um vortice de intensidade no centro. Na esfera
consiste de n vortices unitarios nos vertices de um poligono regular inscrito numa circunferência
em uma latitude fixa da esfera com e sem um vortice de intensidade no polo norte. A ferramenta
basica utilizada e o Teorema do Centro de Lyapunov
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Analysis of a prey-predator model in age-structured population dynamicsEl Idrissi, Omar 17 July 2001 (has links)
No description available.
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The Complexity of angel-daemons and game isomorphismGarcía Chacón, Alina 07 May 2012 (has links)
The analysis of the computational aspects of strategic situations is a basic field in Computer
Sciences. Two main topics related to strategic games have been developed. First,
introduction and analysis of a class of games (so called angel/daemon games) designed
to asses web applications, have been considered. Second, the problem of isomorphism
between strategic games has been analysed. Both parts have been separately considered.
Angel-Daemon Games
A service is a computational method that is made available for general use through a
wide area network. The performance of web-services may fluctuate; at times of stress the
performance of some services may be degraded (in extreme cases, to the point of failure).
In this thesis uncertainty profiles and Angel-Daemon games are used to analyse servicebased
behaviours in situations where probabilistic reasoning may not be appropriate.
In such a game, an angel player acts on a bounded number of ¿angelic¿ services
in a beneficial way while a daemon player acts on a bounded number of ¿daemonic¿
services in a negative way. Examples are used to illustrate how game theory can be used
to analyse service-based scenarios in a realistic way that lies between over-optimism and
over-pessimism.
The resilience of an orchestration to service failure has been analysed - here angels and
daemons are used to model services which can fail when placed under stress. The Nash
equilibria of a corresponding Angel-Daemon game may be used to assign a ¿robustness¿
value to an orchestration.
Finally, the complexity of equilibria problems for Angel-Daemon games has been
analysed. It turns out that Angel-Daemon games are, at the best of our knowledge, the
first natural example of zero-sum succinct games.
The fact that deciding the existence of a pure Nash equilibrium or a dominant strategy
for a given player is Sp
2-complete has been proven. Furthermore, computing the value of
an Angel-Daemon game is EXP-complete. Thus, matching the already known complexity
results of the corresponding problems for the generic families of succinctly represented
games with exponential number of actions.
Game Isomorphism
The question of whether two multi-player strategic games are equivalent and the computational
complexity of deciding such a property has been addressed. Three notions
of isomorphisms, strong, weak and local have been considered. Each one of these isomorphisms
preserves a different structure of the game. Strong isomorphism is defined to
preserve the utility functions and Nash equilibria. Weak isomorphism preserves only the
player preference relations and thus pure Nash equilibria. Local isomorphism preserves
preferences defined only on ¿close¿ neighbourhood of strategy profiles.
The problem of the computational complexity of game isomorphism, which depends
on the level of succinctness of the description of the input games but it is independent
of the isomorphism to consider, has been shown. Utilities in games can be given succinctly
by Turing machines, boolean circuits or boolean formulas, or explicitly by tables.
Actions can be given also explicitly or succinctly. When the games are given in general
form, an explicit description of actions and a succinct description of utilities have been
assumed. It is has been established that the game isomorphism problem for general form
games is equivalent to the circuit isomorphism when utilities are described by Turing Machines;
and to the boolean formula isomorphism problem when utilities are described by
formulas. When the game is given in explicit form, it is has been proven that the game
isomorphism problem is equivalent to the graph isomorphism problem.
Finally, an equivalence classes of small games and their graphical representation have
been also examined.
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[en] A SEQUENTIAL MODEL OF ENDOGENOUS COLLATERAL / [pt] UM MODELO SEQUENCIAL DE COLATERAL ENDÓGENODANIEL CHRITY 09 July 2004 (has links)
[pt] Este trabalho desenvolve e estabelece a existência de
equilíbrio para um modelo sequencial com dois estágios,
mercados financeiros incompletos, risco de crédito e
colateral endógeno. No primeiro estágio, ao escolherem o
colateral, de acordo com uma regra exogenamente
determinada, os agentes emitem ativos personalizados que
serão transacionados no segundo estágio, em uma economia
Walrasiana com dois períodos. A nossa estrutura permite o
surgimento de modelos nos quais os próprios agentes
escolhem suas garantias, de forma similar aos modelos já
existentes de colateral endógeno. Tais modelos exibem o que
podemos chamar de A Maldição do Vencedor, situação na qual
o agente escolhe, racionalmente, oferecer colateral nulo,
inviabilizando, em equilíbrio, a transação de ativos. Com
isso, a economia é jogada para um equilíbrio Pareto
inferior no qual não existem mercados financeiros. Ao
introduzir uma sequencialidade nas escolhas, conseguimos
resolver esse problema, pois os agentes antecipam o efeito
da escolha de colateral sobre os payoffs de equilíbrio,
escolhendo, racionalmente, colaterais positivos. Assim,
conseguimos não somente solucionar uma limitação dos
modelos existentes, como ainda, permitir o surgimento de
inúmeros sub-modelos através das diversas possibilidades
para a regra de escolha na determinação do colateral. / [en] This paper develops and establishes the existence of
equilibrium for a sequential model with two stages,
incomplete financial markets, credit risk and endogenous
collateral. In the first stage, by choosing the collateral,
according to a predetermined and exogenously given rule,
the agents issue personalized securities that will be
traded in the second stage in aWalrasian economy with two
periods. Our structure allows for models in which the
agents choose their own collateral, similar to the existing
endogenous collateral models. Those models exhibit what we
might call, The Winner s Curse, a situation in which the
agent choose, rationally, to offer no collateral, making
asset trading impossible, in equilibrium. The economy is
then thrown in a Paretoinferior equilibria in which there
are no financial markets. By introducing the agent s choice
in a sequential fashion, we avoid such a problem, because
the agents anticipate the effects of their collateral
choice over the equilibrium payoffs, therefore choosing
rationally, positive collateral. That way, we are able, not
only to solve a shortcoming of the existing models, but
also to allow for a variety of sub-models through the
several possible choices for the collateral determining
rule.
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[en] ANALYSIS OF MECHANISMS FOR THE SALE OF GOVERNMENT BONDS FOR PUBLIC FINANCING: A ANALYSIS FROM THE PERSPECTIVE OF AUCTION THEORY / [pt] ANÁLISE DE MECANISMOS DE VENDA DE TÍTULOS PARA O FINANCIAMENTO PÚBLICO: UMA ANÁLISE SOB A ÓTICA DA TEORIA DE LEILÕESLUIZ HENRIQUE AREAS PERES 30 September 2021 (has links)
[pt] Este trabalho tem por objetivo analisar uma das formas de financiamento
da República Federativa do Brasil: a venda de títulos da dívida pública. Para
isso serão analisadas diversas informações oficiais dos órgãos competentes,
relacionadas às regras que permeiam este tipo de negociação. Além disso, serão
explorados trabalhos correlatos e suas principais contribuições. Por fim, o texto
busca mostrar qual formato de leilão é, teoricamente, a mais vantajosa para o
Tesouro Nacional negociar seus títulos de dívida. / [en] This work aims to analyze one of the forms of financing the Federative
Republic of Brazil: the sale of government bonds. For this, varied information from official agencies related to the rules that govern this type of negotiation will be analyzed. In addition, related works and their main contributions will be explored. Finally, the text seeks to show which auction format is, theoretically, the most advantageous for the National Treasury to negotiate its debt securities.
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Coordination and conflict: an experimental approachGürgüç, Zeynep 02 October 2009 (has links)
Esta tesis consta de tres proyectos sobre coordinación y los conflictos utilizando un enfoque experimental. El capítulo 1 estudia si un mecanismo de votación incentiva una coordinación eficiente y concluye en comparación a un sistema de decisión carente de votación (regla del dictador), ambos mecanismos (decisión por mayoría y decisión unánime) son eficaces incentivando la coordinación en la toma de decisiones posteriores. El capítulo 2 se centra en los fallos de coordinación e investiga si una "mancha solar" puede causar un problema de coordinación sobre el equilibrio Pareto-Superior. De los resultados, se deduce que una señal aleatoria exógena genera ineficiencias, aunque sería simplemente mejor ignorarla. Por último, el capítulo 3 estudia un juego de concurso en una red de conflicto. Los resultados demuestran que las estructuras de red en cuestión importan en la determinación del nivel de las inversiones en tecnología de conflicto y, por lo tanto, afectan la intensidad total de los conflictos. / This thesis is a collection of three research projects on coordination and conflict using an experimental approach. Chapter 1 studies whether a voting mechanism induces efficient coordination; and, concludes that compared to a dictator rule where voting is absent, both of the voting rules studied, i.e. majority and unanimity, are successful in inducing coordination in subsequent decisions. Chapter 2 focuses on coordination failures and investigates whether a sunspot leads to failure in coordinating on the Pareto-Superior equilibrium; and in fact, deduces that a random exogenous signal leads to inefficiencies even though it would simply be better if ignored. Finally, chapter 3 studies a contest game in a conflict network. It shows that network structures matter in determining the level of individual investments in the conflict technology, and hence affect total conflict intensity.
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[pt] EQUILÍBRIOS DE NASH EM MERCADOS ELÉTRICOS COM FUNÇÕES DE OFERTA QUADRÁTICAS COTADAS / [en] NASH EQUILIBRIA IN POOL-BASED ELECTRICITY MARKETS WITH BOUNDED QUADRATIC SUPPLY FUNCTIONSMARCELO MORAES RESENDE 20 June 2023 (has links)
[pt] Este trabalho analisa um mercado de eletricidade em que os geradores
declaram funções de custo quadráticas para o operador da rede e também
suas disponibilidades máximas de produção. O operador, então, determina as
quantidades a serem produzidas por cada gerador de modo a atender a uma
demanda inelástica, ao menor custo possível. Estabelecem-se alguns resultados
que permitem computar os equilíbrios de Nash deste modelo e descrevem-se
algumas de suas propriedades, tais como condições de existência. / [en] This work analyzes an electricity market in which generators declare
quadratic cost functions for the grid operator and also the maximum capacity
available. The operator then determines the quantities that each generator
must produce to meet an inelastic demand at the lowest possible cost. Some
results are established that allow computing the Nash equilibria of this model
and some of their properties are described, such as existence conditions.
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