Michael Maschler in Barcelona

Michael Maschler started visiting Spain on a regular basis late in his career. He was already a famous game theorist. As a teacher, he was certainly proud of the mark he had left on generations of students. And he was well aware of his accomplishments as a researcher, but had no trace of arrogance. His favorite activity was to listen to graduate students and learning from them while providing advice, and then to work with anyone who had a worthy project, regardless of the status and age of his collaborators. He made many friends, found several co-authors and left a deep mark in the community of Spanish game theorists during his frequent visits to Alicante, Barcelona, Bilbao and Santiago. His extended stays at the Autònoma started by a ritual: we would go together to buy a substantial stock of Coke Light, to be jointly consumed during our discussions involving work, our families and our countries. He was already into his late sixties when he started visiting us, but nobody could follow his working pace. He was once locked into the department for several hours of the night prior to his departure: our security guards could not imagine anyone staying in the office that late! We shared a common interest for the elusive and hard problem of coalition formation. In addition to its obvious interest, this problem is an excellent meeting ground for the cooperative and the non-cooperative points of view. We agreed on the fact that the divorce between these two approaches was unnecessary and that game theory could fruitfully benefit from their combination, a point recently made by Eric Maskin in the Nobel Laureates’ roundtable at the Game Theory Society meetings in Evanston. Much of our discussions remain unpublished in the form of incomplete notes, since the question is tough, even when properly simplified. Yet, we managed to complete and to publish one paper (in cooperation with Jonathan Shalev). It leans mostly toward the non-cooperative side, though it led to further work of Michael with Granot and Shalev on a more cooperative note. As a social choice theorist, I had observed that new forms of strategic voting can arise when we move from a static to a dynamic setting. For example, one may postpone the admission of a candidate into a club when membership carries the right to participate in later admittance decisions. Indeed, I may like someone’s abilities but not this person’s taste, and this may lead me to only allow this person to enter when other important decisions have already been made. Similarly, one can force the arrival of some new members in order to reinforce alliances. I told Michael about the general problem during a stroll, and in a few hours he had developed a very simple model that gave us a start, while also qualifying our objectives. I had dreamed of a general theory of the evolution of clubs (and societies in general) as a function of their admission