1,721,027 research outputs found
New results on equilibria in strategic candidacy
No full textWe consider a voting setting where candidates have preferences about the outcome of the election and are free to join or leave the election. The corresponding candidacy game, where candidates choose strategically to participate or not, has been studied in very few papers, mainly by Dutta et al. [5,6], who showed that no non-dictatorial voting procedure satisfying unanimity is candidacy-strategy-proof, or equivalently, is such that the joint action where all candidates enter the election is always a pure strategy Nash equilibrium. They also showed that for voting trees, there are candidacy games with no pure strategy equilibria. However, no results were known about other voting rules. Here we prove several such results. Some are positive (a pure strategy Nash equilibrium is guaranteed for Copeland and the uncovered set, whichever is the number of candidates, and for all Condorcet-consistent rules, for 4 candidates). Some are negative, namely for plurality and maximin
Taxed Congestion Games with Failures
No full textIn this paper, we introduce and study Taxed Congestion Games with Failures [TCGFs], extending congestion games with failures [CGFs] to consider costly task submission. We define TCGFs, and prove that TCGFs possess a pure strategy equilibrium. Moreover, we provide an efficient algorithm for the computation of such equilibrium. We also provide a specialized, simpler, algorithm for the case in which all resources are identical
Random order congestion games
No full textWe introduce a new class of games, Random Order Congestion Games [ROCGs]. In an ROCG, each player has a task that can be carried out by any element of a set of resources, and each resource executes its assigned tasks in a random order. Each player's aim is to minimize his expected cost which is the sum of two terms---the sum of the fixed costs over the set of his utilized resources and the expected cost of his task execution. The cost of a player's task execution is determined by the earliest time his task is completed, and thus it might be beneficial for him to assign his task to several resources. We prove the existence of pure strategy Nash equilibria in ROCGs. Moreover, we present a polynomial time algorithm for finding such an equilibrium in a given ROCG
Taxation and stability in cooperative games
No full textCooperative games are a useful framework for modeling multi-agent behavior in environments where agents must collaborate in order to complete tasks. Having jointly completed a task and generated revenue, agents need to agree on some reasonable method of sharing their profits. One particularly appealing family of payoff divisions is the core, which consists of all coalitionally rational (or, stable) payoff divisions. Unfortunately, it is often the case that the core of a game is empty, i.e. there is no payoff scheme guaranteeing each group of agents a total payoff higher than what they can get on their own. As stability is a highly attractive property, there have been various methods of achieving it proposed in the literature. One natural way of stabilizing a game is via taxation, i.e. reducing the value of some coalitions in order to decrease their bargaining power. Existing taxation methods include the ε-core, the least-core and several others. However, taxing coalitions is in general undesirable: one would not wish to overly tamper with a given coalitional game, or overly tax the agents. Thus, in this work we study minimal taxation policies, i.e. those minimizing the amount of tax required in order to stabilize a given game. We show that games that minimize the total tax are to some extent a linear approximation of the original games, and explore their properties. We demonstrate connections between the minimal tax and the cost of stability, and characterize the types of games for which it is possible to obtain a tax-minimizing policy using variants of notion of the ε-core, as well as those for which it is possible to do so using reliability extensions. Copyright © 2013, International Foundation for Autonomous Agents and Multiagent Systems (www.ifaamas.org). All rights reserved
Avoiding regret in an agent-based asset pricing model
No full textWe use an agent-based asset pricing model to test the implications of the disposition effect (avoiding regret) on investors’ interactions and price settings. We show that it has a direct impact on the returns series produced by the model, altering important stylized facts such as its heavy tails and volatility clustering. Moreover, we show that the horizon over which investors compute their wealth has no effect on the dynamics produced by the model
Auction mechanisms for demand-side intermediaries in online advertising exchanges
No full textMotivated by the online advertising exchange marketplace where demand-side intermediaries conduct local upstream auctions and participate in the exchanges’ real-time auctions, we study the revenue and efficiency effects of three different auction mechanisms for such intermediaries. Specifically, we consider the widely-used first-price sealed-bid auction and two variations of the Vickrey auction (termed pre- and post-award), in a single-exchange single item setting. We show that, for a homogeneous population of intermediaries with captive buyers competing at the exchange, the three mechanisms yield different expected profits for the intermediaries and revenue for the exchange, but a complete ranking for all mechanisms cannot be attained. We also demonstrate that the optimal reserve price of the exchange increases with the number of buyers and/or intermediaries, and that the social welfare decreases, compared to classical auctions without intermediaries. Moreover, we show that pre-award Vickrey auctions are less efficient than the other mechanisms. Finally, we compare the two Vickrey variations in a duopoly setting with non-captive buyers, and show that all buyers always select the post-award mechanis
Strategic Candidacy Games with Lazy Candidates
No full textIn strategic candidacy games, both voters and candidates have preferences over the set of candidates, and candidates may strategically withdraw from the election in order to manipulate the outcome according to their preferences. In this work, we extend the standard model of strategic candidacy games by observing that candidates may find it costly to run an electoral campaign and may therefore prefer to withdraw if their presence has no effect on the election outcome. We study the Nash equilibria and outcomes of natural best-response dynamics in the resulting class of games, both from a normative and from a computational perspective, and compare them with the Nash equilibria of the standard model
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