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In sponsored search auctions, advertisers compete for a number of available advertisement slots of different quality. The auctioneer decides the allocation of advertisers to slots using bids provided by them. Since the advertisers may act strategically and submit their bids in order to maximize their individual objectives, such an auction naturally defines… (More)

- Ioannis Caragiannis, Christos Kaklamanis, Panagiotis Kanellopoulos, Maria Kyropoulou
- Theory of Computing Systems
- 2009

In this paper we study the impact of fairness on the efficiency of allocations. We consider three different notions of fairness, namely proportionality, envy-freeness, and equitability for allocations of divisible and indivisible goods and chores. We present a series of results on the price of fairness under the three different notions that quantify the… (More)

We study the effect of combining selfishness and altruism in atomic congestion games. We allow players to be partially altruistic and partially selfish and determine the impact of this behavior on the overall system performance. Surprisingly, our results indicate that, in general, by allowing players to be (even partially) altruistic, the overall system… (More)

- Ioannis Caragiannis, Christos Kaklamanis, +4 authors Éva Tardos
- J. Economic Theory
- 2015

The Generalized Second Price (GSP) auction is the primary auction used for monetizing the use of the Internet. It is well-known that truthtelling is not a dominant strategy in this auction and that inefficient equilibria can arise. Edelman et al. and Varian show that an efficient equilibrium always exists in the full information setting. Their results,… (More)

Sponsored search auctions are the main source of revenue for search engines. In such an auction, a set of utility-maximizing advertisers compete for a set of ad slots. The assignment of advertisers to slots depends on bids they submit; these bids may be different than the true valuations of the advertisers for the slots. Variants of the celebrated VCG… (More)

We present a simple algorithm for the maximum spanning star forest problem. We take advantage of the fact that the problem is a special case of complementary set cover and we adapt an algorithm of Duh and Fürer in order to solve it. We prove that this algorithm computes 193/240 ≈ 0.804-approximate spanning star forests; this result improves a previous lower… (More)

We study the strategic considerations of miners participating in the bitcoin's protocol. We formulate and study the stochastic game that underlies these strategic considerations. The miners collectively build a tree of blocks, and they are paid when they create a node (mine a block) which will end up in the path of the tree that is adopted by all. Since the… (More)

We study the problem of allocating a set of indivisible items to players having additive utility functions over the items. We consider allocations in which no player envies the bundle of items allocated to the other players too much. We present a simple proof that deterministic truthful allocations do not minimize envy by characterizing the truthful… (More)

The seminal work of Myerson (Mathematics of OR ’81) characterizes incentive-compatible single-item auctions among bidders with independent valuations. In this setting, relatively simple deterministic auction mechanisms achieve revenue optimality. When bidders have correlated valuations, designing the revenue-optimal deterministic auction is a… (More)

- Yiannis Giannakopoulos, Maria Kyropoulou
- WINE
- 2015

We study the problem of scheduling m tasks to n selfish, unrelated machines in order to minimize the makespan, where the execution times are independent random variables, identical across machines. We show that the VCG mechanism, which myopically allocates each task to its best machine, achieves an approximation ratio of O ( ln n ln ln n ) . This improves… (More)