Author name cluster

Lisa Rey

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4 papers

2 author rows

JAIR Journal 2022 Journal Article

Altruistic Hedonic Games

Anna Maria Kerkmann
Nhan-Tam Nguyen
Anja Rey
Lisa Rey
Jörg Rothe
Lena Schend
Alessandra Wiechers

Hedonic games are coalition formation games in which players have preferences over the coalitions they can join. For a long time, all models of representing hedonic games were based upon selfish players only. Among the known ways of representing hedonic games compactly, we focus on friend-oriented hedonic games and propose a novel model for them that takes into account not only the players’ own preferences but also their friends’ preferences. Depending on the order in which players look at their own or their friends’ preferences, we distinguish three degrees of altruism: selfish-first, equal-treatment, and altruistic-treatment preferences. We study both the axiomatic properties of these games and the computational complexity of problems related to various common stability concepts.

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AAAI Conference 2019 Conference Paper

Generalized Distance Bribery

Dorothea Baumeister
Tobias Hogrebe
Lisa Rey

The bribery problem in elections asks whether an external agent can make some distinguished candidate win or prevent her from winning, by bribing some of the voters. This problem was studied with respect to the weighted swap distance between two votes by Elkind et al. (2009). We generalize this definition by introducing a bound on the distance between the original and the bribed votes. The distance measures we consider include a restriction of the weighted swap distance and variants of the footrule distance, which capture some realworld models of influence an external agent may have on the voters. We study constructive and destructive variants of distance bribery for scoring rules and obtain polynomial-time algorithms as well as NP-hardness results. For the case of element-weighted swap and element-weighted footrule distances, we give a complete dichotomy result for the class of pure scoring rules.

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AAMAS Conference 2016 Conference Paper

Altruistic Hedonic Games

Nhan-Tam Nguyen
Anja Rey
Lisa Rey
Jörg Rothe
Lena Schend

Hedonic games are coalition formation games in which players have preferences over the coalitions they can join. All models of representing hedonic games studied so far are based upon selfish players only. Among the known ways of representing hedonic games compactly, we focus on friend-oriented hedonic games and propose a novel model for them that takes into account not only a player’s own preferences but also her friends’ preferences under three degrees of altruism. We study both the axiomatic properties of these games and the computational complexity of problems related to various stability concepts.

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ECAI Conference 2016 Conference Paper

Minisum and Minimax Committee Election Rules for General Preference Types

Dorothea Baumeister
Toni Böhnlein
Lisa Rey
Oliver Schaudt
Ann-Kathrin Selker

In committee elections it is often assumed that voters only (dis)approve of each candidate or that they rank all candidates, as it is common for single-winner elections. We suggest an intermediate approach, where the voters rank the candidates into a fixed number of groups. This allows more diverse votes than approval votes, but leaves more freedom than in a linear order. A committee is then elected by applying the minisum or minimax approach to minimize the voters' dissatisfaction. We study the axiomatic properties of these committee election rules as well as the complexity of winner determination and show fixed-parameter tractability for our minimax rules.

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