In 2020, Ioannis Caragiannis started as Professor in the Computational Complexity and Game Theory research group at the Department of Computer Science

Research area and vision

At the department, Ioannis will follow and expand his research agenda at the interface of computer science and economics. Specific problem areas include fair division, with a focus on new fairness concepts for allocations of indivisible items and their computational complexity, multi-winner voting rules and their use as simple algorithms for decision-making, and the design and analysis of machine learning tasks that are robust to strategic behaviour of data providers. These are indicative examples of a modern toolset the algorithm designer should have available today. Ioannis plans to extensively disseminate this toolset to students and young colleagues as part of an effort to nurture a new generation of algorithm designers at AU.

Academic background

Before joining Aarhus University, Ioannis was a faculty member at the University of Patras (since 2006). His research interests include the design and analysis of algorithms, economics and computation, and foundations of machine learning and artificial intelligence. His teaching experience includes core courses on algorithms and computational complexity and advanced electives or graduate courses on algorithmic game theory, online computation, approximation algorithms, and more. He has published more than 160 papers in conference proceedings, scientific journals, and books and has participated in basic research projects funded by the European Commission and the Greek state. He regularly serves as a program committee member in conferences at the interface of theoretical computer science, artificial intelligence, and economics, such as the ACM Conference on Economics and Computation (EC) and the AAAI Conference on Artificial Intelligence (AAAI). Currently, he is the organizer and program co-chair of the 14th International Symposium on Algorithmic Game Theory (SAGT) that will take place in Aarhus in September 2021.

Important achievements in the past

In a nutshell, his most important achievements are the following:

• His work on fair division is probably his major success. His EC 2016/TEAC paper on the many fairness properties of the maximum Nash welfare allocation has already received more than 250 citations. In another influential paper, he introduced the notion of the price of fairness to quantify the welfare loss in allocations due to fairness.
• He has also studied voting rules in terms of their adequacy for effective decision-making. Can a voting rule discover an underlying ground truth assuming that the votes are noisy estimates of this ground truth? How effective is a voting rule in selecting the alternative of optimal value for the voters? Ioannis and his colleagues examined voting rules in terms of their distortion, a notion that has received much attention recently.
• Also, together with his colleagues, they presented the first results for computing approximate pure Nash equilibria in (unweighted and weighted) congestion games.
• Finally, his work on the price of anarchy (of load balancing games and generalized second-price auctions) has received much attention from the algorithmic game theory community.

Top 3 publications

• Ι. Caragiannis, D. Kurokawa, H. Moulin, A. D. Procaccia, N. Shah, and J. Wang. The unreasonable fairness of the maximin Nash welfare. ACM Transactions on Economics and Computation, 7(6), article 12, 2019. Preliminary version in Proceedings of the 17^th ACM Conference on Economics and Computation (EC), pages 305–322, 2016.
• I. Caragiannis, C. Kaklamanis, P. Kanellopoulos, M. Kyropoulou, B. Lucier, R. Paes Leme, and E. Tardos. Bounding the inefficiency of outcomes in generalized second price auctions. Journal of Economic Theory, 156, pages 343-388, 2015.
• C. Boutilier, I. Caragiannis, S. Haber, T. Lu, A. D. Procaccia, and O. Sheffet. Optimal social choice functions: a utilitarian view. Artificial Intelligence, 227, pages 190–213, 2015. Preliminary version in Proceedings of the 13^th ACM Conference on Electronic Commerce (EC), pages 194–214, 2012.