Social networks constitute a major channel for the diffusion of information and the formation of attitudes in a society. Introducing a dynamic model of social learning, the first part of this thesis studies the emergence of socially influential individuals and groups, and identifies the characteristics that make them influential. The second part uses a Bayesian network game to analyse the role of social interaction and conformism in the making of decisions whose returns or costs are ex ante uncertain.

The first chapter of this thesis considers a contractual principal-agent relationship in an unstable environment. The players are uncertain whether repeated interaction is possible. I examine the role that the deliberate choice of an incomplete (non-verifiable and unenforceable) contract plays in signalling stability and trust. In this model, contractors may privately observe shocks that force them to end the relationship after the current period. Complete (verifiable) contracts, which are assumed to be feasible, ensure cooperation in compliance with the contract. With incomplete contracts, the players make themselves vulnerable to exploitation by their partners. But if cooperation occurs notwithstanding, the contractors update their beliefs about each other’s willingness to interact again. When the agent observes that her partner and herself are able to continue the relationship, she undertakes a non-contractible, mutually beneficial investment. The second chapter is based on the theory by Hart and Moore (QJE, 2008) that regards contracts as reference points for feelings of entitlement. Parties’ ex post performance depends on whether they receive what they feel entitled to, which is assumed to be the best possible outcome permitted by the contract. Consequentially, there exists a trade-off between contractual flexibility (agreement on a price interval) and rigidity (agreement on a single price). Hart and Moore do not analyse the role that third party contract enforcement plays for parties’ feelings of entitlement, shading on performance and contract choice. I demonstrate that Hart and Moore’s results rely on a number of assumptions that can be challenged when incorporating litigation into the model. They assume that trade is voluntary but renegotiation is prohibited. I argue that either trade is voluntary but renegotiation is possible or courts compel parties to trade according to the contract. In the former scenario, fixed price contracts may not act as reference points and the parties feel entitled to the best possible outcomes from renegotiation. In the latter scenario, contracts may act as reference points because of the option of contract enforcement. However, potential flexibility incorporated in the contract is lost. The third chapter provides an experimental examination of the effect of contract enforcement on contractors’ reference points for feelings of entitlement. Previous experiments by Fehr, Hart and Zehnder (AER 2011) analyse and support the theory by Hart and Moore (QJE, 2008) that contracts are reference points. Both theory and experiments ignore the role of contract enforcement for contractors’ feelings of entitlement. I replicate and confirm Fehr, Hart and Zehnder’s baseline experiment. I also run an additional treatment in which buyers can offer sellers more or less favourable prices than specified in the contract, whereas sellers can request enforcement of contracts as written. I find that contract enforcement matters, without being invoked, for sellers’ punishment behaviour through feelings of entitlement. Without explicit contract enforcement, flexible contracts (agreement on a price range instead of a single price) leave sellers feel entitled to the best possible price permitted by the contract. However, buyers rarely offer such a price which leads to disappointment and punishment. With the option of contract enforcement, sellers feel entitled to the price which the court would enforce, even if it is equally unfavourable than in the no court treatment. The presence of the court provides an outside validation for which prices are reasonable and thereby limits disappointment and punishment.

This thesis is composed of three chapters. Chapter 1 considers the existence of equilibria in games with complete information, where players may have non-ordered and discontinuous preferences. Chapter 2 studies the issues on the existence of pure and behavioral strategy equilibria in games with incomplete information and discontinuous payoffs. We consider the standard setting with Bayesian preferences as well as the case in which players may face ambiguity. Chapter 3 extends the classical results on the Walras-core existence and equivalence to an ambiguous asymmetric information economy, where agents maximize maximin expected utilities (MEU). These results are based on the papers He and Yannelis (2014, 2015a,b,c, 2016a,b). In the first chapter, we propose the condition of "continuous inclusion property" to handle the difficulty of discontinuous payoffs in various general equilibrium and game theory models. Such discontinuities arise naturally in economic situations, including auction, price competition of firms and also patent races. Based on the continuous inclusion property, we establish the equilibrium existence result in a very general framework with discontinuous payoffs. On one hand, this condition is sufficiently general from the methodological point of view, as it unifies almost all special conditions proposed in the literature. On the other hand, our condition is also potentially useful from the realistic point of view, as it could be applied to deal with many economic models which cannot be studied before because of the presence of the discontinuity. In the second chapter, I study the existence problem of pure and behavioral strategy equilibria in discontinuous games with incomplete information. The framework of games with incomplete information is standard as in the literature, except for that we allow players' payoffs to be discontinuous. We illustrate by examples that the Bayesian equilibria may not exist in such games and the previous results are not applicable to handle this problem. We propose some general conditions to retain the existence of both pure strategy and behavioral strategy Bayesian equilibrium, and show that our condition is tight. In addition, we study the equilibrium existence problem in discontinuous games under incomplete information and ambiguity, and show that the maximin framework solves the equilibrium existence issue without introducing any additional condition. In the last chapter, I study a general equilibrium model with incomplete information by adopting the maximin expected utilities. The model is powerful enough to describe the behaviors of risk averse agents that cannot be explained by the standard assumption of subjective expected utilities. I use this new formulation to extend many classical results in general equilibrium theory by incorporating ambiguity into the model. In addition, the desirable incentive compatibility property is shown in our model with maximin expected utilities, while this property will typically fail in the traditional setup. Specifically, the existence results are shown for various equilibrium notions in a general equilibrium model, and the incentives can be guaranteed when all agents use the maximin expected utilities.

An increasing number of parameter estimation tasks involve the use of at least two information sources, one complete but limited, the other abundant but incomplete. Standard algorithms such as EM (or em) used in this context are unfortunately not stable in the sense that they can lead to a dramatic loss of accuracy with the inclusion of incomplete observations. We provide a more controlled solution to this problem through differential equations that govern the evolution of locally optimal solutions (fixed points) as a function of the source weighting. This approach permits us to explicitly identify any critical (bifurcation) points leading to choices unsupported by the available complete data. The approach readily applies to any graphical model in O(n^3) time where n is the number of parameters. We use the naive Bayes model to illustrate these ideas and demonstrate the effectiveness of our approach in the context of text classification problems.

Abstract In an ideal world, the agents would write a contingent contract specifying exactly which outcome is to be implemented in each state. However, the bounded rationality, the contracting agents may be unable to define ex ante the contingencies, and the transaction costs, the costs result from the difficulty of foreseeing contingencies, writing and enforcing contract, will lead to R&D cooperative contracts incomplete essentially. When R&D cooperative contracts are incomplete, the contracting agents face the hazard of ex post opportunistic behavior: each agent may engage in inefficient R&D investment in an attempt to ¡§hold up¡¨ other agents and to obtain a large share of the available quasi-rents. The purposes of this dissertation are to show that the mechanism design to the hold-up problem may implement in incomplete R&D cooperative contracts. In chapter II, we assume that the agents commit not to renegotiate ex post and set up a sequential mechanism. Under this sequential mechanism, the seller (university) sends massages (seller¡¦s true type) to the buyer (firm) who receives the massages and decides whether he will challenge them. The monetary transfer from the buyer to the seller and the quality of trade are the function of agents¡¦ true type. The great merit of this mechanism is that the seller and the buyer play the subgame perfect equilibrium in which both of them announce truthfully. We release the assumption that the contracting agents commit not to renegotiate ex post in chapter III. Under the current legal system, there is nothing to stop buyers or sellers to prevent renegotiation of their original contract. More importantly, the agents will rationally anticipate any renegotiation and this will change the equilibrium strategies of the mechanism itself. According to proposition 3-2, we demonstrate that the direct-revelation mechanism with Rubinsteinian bargaining game induced buyer and seller both announcing honestly but the R&D investment offered by agents were lower than the first best. To avoid the effect generated by renegotiation, some economists argued that the contract in which either buyer or seller has all the ex post bargaining power can induce efficient investment, and thus can implement the first best. This argument contrasts to Aghion and Tirole(1986), for they argued that whether the buyer or the seller should own the innovation hinged on the marginal efficiency of the buyer¡¦s investment compared with that of the seller¡¦s effort. Hence, we accept the property rights concepts proposed by Barzel(1989) and show that the agents can actually raise their payoff by using a mechanism in which performs the function analogous to the real option.

In new economics such as high-tech, knowledge-driven industries, the competitive game changes frequently and dramatically. Two maxims are widely accepted in these markets: 1. it pays to hit the market first. 2. it pays to have superb technology. These industries face a high change and high speed competitive business environment. Information systems of these firms often have to be modified or created based on imprecise requirements or even conceptual ideals. According to past research literature, precise requirement is one of the key success factors for software development outsourcing. Imprecise requirements indicate uncertain project scope and tend to risk. This research of imprecise requirement software development outsourcing base on Adaptive Software Development and Incomplete Contract theory. A case study is used to analyze below imprecise requirement software outsoucing issues issues in a semiconductor foundry MES project: 1. How to deliver a usable system to achieve project goals from imprecise requirements? 2. How to manage frequent change ascribed to imprecise requirements? 3. How to manage project escalation and cost issue ascribed to imprecise requirement?

This dissertation consists of three essays in Economic Theory. The rst essay proposes and studies a new solution concept for games with incomplete information. In game theory, there is a basic methodological dichotomy between Harsanyi's \game-theoretic" view and Aumann's \Bayesian decision-theoretic" view of the world. We follow the game theoretic view, propose and study interim partially correlated rationalizability for games with incomplete information. We argue that the distinction between this solution concept and the interim correlated rationalizability studied by Dekel, Fudenberg and Morris (2007) is fundamental, in that the latter implicitly follows Aumann's Bayesian view. Our main result shows that two types provide the same prediction in interim partially correlated rationalizability if and only if they have the same in nite hierarchy of beliefs over conditional beliefs. We also establish an equivalence result between this solution concept and the Bayesian solution{a notion of correlated equilibrium proposed by Forges (1993). The second essay studies the relationship between correlated equilibrium the redundancy embedded in type spaces. The Bayesian solution is a notion of correlated equilibrium proposed by Forges (1993), and hierarchies of beliefs over conditional beliefs are introduced by Ely and Peski (2006) in their study of interim rationalizability. We study the connection between the two concepts. We say that two type spaces are equivalent if they represent the same set of hierarchies of beliefs over conditional beliefs. We show that the correlation embedded in equivalent type spaces can be characterized by partially correlating devices, which send correlated signals to players in a belief invariant way. Since such correlating devices also implement the Bayesian solution, we establish that the Bayesian solution is invariant across equivalent type spaces. The third essay studies the existence of equilibria for rst-price sealed bid auctions when bidders form a network and each bidder observes perfectly their neighbors' private valuations. Asymmetry in bidders' positions in the network creates asymmetry in bidders' knowledge. We show the existence of pure-strategy equilibrium. / text

Darbą atliko Vilniaus pedagoginio universiteto neakivaizdinių magistrantūros studijų absolventas Rimas Gaidamavičius. Darbo tema – „Moksleivių ugdymas nepilnose šeimose: problemos ir perspektyvos“. Darbo tikslas - išanalizuoti moksleivių ugdymo nepilnose šeimose problemas ir perspektyvas. Bendrasis vaikų ir jaunimo ugdymas – tai pagrindinė nuosekliojo švietimo grandis, asmens tolesnio lavinimosi ir būsimos veiklos pamatas. Bendrojo vaikų ir jaunimo ugdymas – tai pagrindinė nuosekliojo švietimo grandis, asmens tolesnio lavinimosi ir būsimos veiklos pamatas. Bendrojo vaikų ir jaunimo ugdymo paskirtis – kartu su šeima padėti gimtosios kultūros erdvėje atsiskleisti asmens individualybei, parengti asmenį darniam socialiniam gyvenimui. Ugdymas yra asmenybę kuriantis žmonių bendravimas, sąveikaut su aplinka bei žmonijos kultūros vertybėmis Ugdymo apimtis labai didelė, nes ugdymas yra sudėtingas, įvairiapusis ir visuminis procesas, apimantis augimą, švietimą, mokymą, lavinimą, auklėjimą. t.y. asmenybės formavimą. Šeima yra pirmoji ir svarbiausioji ugdymo institucija, nes joje vaikas perima pažiūras, įpročius, kultūrines dvasines vertybes, gauna pirmuosius orientavimosi socialinėje aplinkoje įgūdžius. Ugdymo sėkmė šeimoje priklauso nuo tėvų gebėjimo organizuoti ugdymo procesą, psichologinio mikroklimato šeimoje, realių šeimos galimybių. Tik bendradarbiaudamos šeima ir mokykla gali užtikrinti visapusiškos kryptingos asmenybės vystymąsi. Tyrimo metu iškeltos trys hipotezės. Pirmoji... [toliau žr. visą tekstą] / The paper was written by Rimas Gaidamavičius, valedictorian of Vilnius Pedagogical University of extramural master studies. The theme of the paper – „Education of Children in Incomplete Families: Problems and Perspectives". The aim of the paper – analyse the problems and perspectives of education of children in the incomplete families. The common education of children and youth is the most important chain of education, the fundamental of person‘s further training and activity. The aim of general education of children and youth together with the family is to reveal person‘s individuality in the space of native culture, formulate person for the harmonious social life. Education is the formulation of the person by communication in the interaction with the environment and valuables of human culture. The scope of education is very big because the education is a very complex process comprising growing, education, training and human‘s identity‘s formation. Family is the very first and the most important institution of education as the child absorbs the attitude, traditions, cultural and spiritual values, gets the very first orientation in the social environment right from its parents. The success of education in the family depends upon the ability of parents to organize the process of education, psychological microclimate in the family and real possibilities of the family. Only through the interaction of the family and school the overall education of a person might be warranted... [to full text]

In this abstract, we present a nonlinear curvelet-based sparsity promoting formulation of a seismic processing flow, consisting of the following steps: seismic data regularization and the restoration of migration amplitudes. We show that the curvelet’s wavefront detection capability and invariance under the migration-demigration operator lead to a formulation that is stable under noise and missing data.

This paper solves a long-standing open problem in mathematical finance: to find a solution to the problem of maximizing utility from terminal wealth of an agent with a random endowment process, in the general, semimartingale model for incomplete markets, and to characterize it via the associated dual problem. We show that this is indeed possible if the dual problem and its domain are carefully defined. More precisely, we show that the optimal terminal wealth is equal to the inverse of marginal utility evaluated at the solution to the dual problem, which is in the form of the regular part of an element of(L∞)* (the dual space of L∞). (author's abstract) / Series: Working Papers SFB "Adaptive Information Systems and Modelling in Economics and Management Science"