Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Diss. Göteborg : Göteborgs universitet, 2008.

Thesis (M.C.S.)--Carleton University, 1998. / Also available in electronic format on the Internet.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 58-59). Also available in electronic version.

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Η εργασία χωρίζεται σε δυο βασικά μέρη. Στο πρώτο μέρος αναφερόμαστε στα παίγνια γενικού αθροίσματος δυο παιχτών, όπου μετά την αναφορά της βασικής θεωρίας και μιας περιγραφής στις δομές που επικρατούν στις αγορές, γίνεται παρουσίαση στα μοντέλα διπωλίου του Cournot, του Betrand και του Stackelberg. Στο δεύτερο μέρος αναφερόμαστε σε παίγνια με συμμαχίες και πως προσεγγίζονται τότε οι αμοιβές των παιχτών και η αξία τους στο παίγνιο. / This report is seperated in two sections. In the first section we refer in general sum games with two players, where since we report the general theory and an analysis of market structure we present the duopoly models of Cournot, Bertrand and Stackelberg. In the second part we refer in games in coalitional form and how we can calculate the profits and the values of the players in such games

This thesis includes three essays exploring some economic implications of queueing. A preliminary chapter introducing useful results from the literature which help contextualize the original research in the thesis is presented first. This introductory chapter starts by surveying queueing results from probability theory and operations research. Then it covers a few seminal papers on strategic queueing, mostly but not exclusively from the economics literature. These cover issues of individual and social welfare in the context of First Come First Served (FCFS) and Equitable Processor Sharing (EPS) queues, with one or multiple servers, as well as a discussion of strategic interactions surrounding queue cutting. Then an overview of some important papers on the impact of queueing on competitive behaviour, mostly Industrial Organization economists, is presented. The first original chapter presents a model for the endogenous determination of the number of queues in an M/M/2 system. Customers arriving at a system where two customers are being served play a game, choosing between two parallel queues or one single queue. Subgame perfect equilibria are obtained, varying with customer characteristics and game specifications. With risk neutrality and when jockeying is not permitted, a single queue is an equilibrium, as is two queues. With risk neutrality and jockeying allowed, there is a unique two queue equilibrium. With risk aversion and no jockeying, there is a unique single queue equilibrium, and with risk aversion and jockeying, the equilibrium depends on the magnitude of risk aversion. The second chapter analyses the individual decisions taken by consumers when deciding whether to join an M/M/1 queue where a subset of customers who interact repeatedly can both cut the queue and be overtaken once they join, by-passing occasional users. This is shown to be an equilibrium in repeated games for sufficiently patient customers. The expected sojourn time for customers under this discipline is described as a solution of a system of difference equations, and this is then used to obtain a threshold joining strategy for arrivals, which is independent of the number of regular customers in the queue, as regulars form a sub-queue under the LCFS discipline. Numerical methods are then employed to contrast sojourn times and thresholds with the equilibrium for a strict First Come First Served queueing discipline, and with the socially optimal joining rule. Finally, the third chapter describes a duopoly market for healthcare where one of the two providers is publicly owned and charges a price of zero, while the other sets a price so as to maximize its profit. Both providers are subject to congestion in the form of an M/M/1 queue, and they serve patient-customers with randomly distributed unit costs of time. Consumer demand (as market share) for both providers is obtained and described with its full complement of comparative statics. The private provider’s pricing decision is explored, and equilibrium existence is proven. Social welfare functions are described and the welfare maximizing condition obtained. Numerical simulations with uniform and Kumaraswamy distributions are performed for several parameter values, showcasing the pricing provider’s decision and its relationship with social welfare.

Blockchain techniques have received an outburst of interest both in academia and industry, with numerous benefits such as decentralization, persistency, anonymity and auditability. There has been widespread adoption of blockchain in various fields ranging from cryptocurrency, financial services, risk management, internet of things (IoT) to public and social services. As a distributed ledger, blockchain records data in the form of linked blocks secured by cryptography. Instead of being controlled by a central third party like a bank, this ledger is maintained by a P2P network. To work properly, it is essential that the nodes in the network have the same local view of the ledger. A consensus mechanism is the core of a blockchain system since it regulates how to achieve the same states among the nodes in a distributed fashion. Specifically, it grants a qualified miner the right of appending the ledger in a period of time. Despite its potential as a disruptive technology, blockchain is currently facing multiple challenges and problems, which incurs some issues on the performance, security, and fairness of blockchain-based systems. There are many underlying reasons for those challenges and problems, such as an inefficient networking protocol, a time-consuming consensus algorithm, a strategic mining node and so on. In this dissertation, we summarize our theoretical studies on the above-mentioned topic from three different aspects. Details are as follows: Design: A major weakness of the current blockchain systems is the low transaction throughput, which is resulted from the small block size, the long block generation time, and the delayed block propagation. To shorten the block propagation delay, we design a neighbor selection algorithm, improving the communication speed in the P2P network of the blockchain. This design is an attempt on topology optimization and reduces the frequency of blockchain forking. Forking is a situation where the blockchain temporarily diverges into two or more branches, which wastes mining power and causes security issues. Extension: Although a consensus mechanism aims to regulate mining nodes’ behavior, it also can be manipulate by strategic miners within legal limits due to their profit-driven nature. In the dissertation, we analyze strategies that miners apply for utility maximization under different consensus mechanisms from the perspective of game theory. And then we propose distributed algorithms to optimize resource allocation among miners. Application: We also propose a blockchain-based market where we believe the application of blockchain will enhance the corresponding applications. It is a blockchain-powered data market that allows multi-user cooperative search. We also integrate smart contract into these applications. All discussions in this dissertation are theoretical explorations. The theoretical results may not be realistically practical since we hold strong assumptions. We hope that, we could fill the gap between theory and practice in the future. / Computer and Information Science

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