10:00 | Arianna Novaro's PhD Defence - Collective Decision Making with Goals
13:00 | Lunch
15:00 | Gabriella Pigozzi (Paris-Dauphine University) - An opinion diffusion model with deliberation
We propose an agent-based model of group decision-making, where discussions happen in dyadic inter-individual steps and moments of collective argumentative deliberation. Agents are argumentative vigilant, as they do not change opinion unless some justification is given to them. We study the evolution and convergence of opinions, the presence of extremism, and the correctness of decisions taken within the deliberating population. (Joint work with George Butler and Juliette Rouchier).
15:40 | Edith Elkind (University of Oxford) - Protecting Elections by Recounting Ballots
Complexity of voting manipulation is a prominent topic in computational social choice. In this work, we consider a two-stage voting manipulation scenario. First, a malicious party (an attacker) attempts to manipulate the election outcome in favor of a preferred candidate by changing the vote counts in some of the voting districts. Afterwards, another party (a defender), which cares about the voters' wishes, demands a recount in a subset of the manipulated districts, restoring their vote counts to their original values. We investigate the resulting Stackelberg game for the case where votes are aggregated using two variants of the Plurality rule, and obtain an almost complete picture of the complexity landscape, both from the attacker's and from the defender's perspective.
16:20 | Coffee break
16:40 | Nicolas Maudet (Sorbonne University) - House Markets and Single-Peaked Preferences: From Centralized to Decentralized Allocation Procedures
Recently, the problem of allocating one resource per agent with initial endowments (house markets) has seen a renewed interest: indeed, while in the general domain Top Trading Cycle is known to be the only procedure guaranteeing Pareto-optimality, individual rationality, and strategy proofness, the situation differs in single-peaked domains. Bade (2019) presented the Crawler, an alternative procedure enjoying the same properties (with the additional advantage of being implementable in obviously dominant strategies); while Damamme et al. (2015) showed that allowing mutually beneficial swap-deals among the agents was already enough to guarantee Pareto-optimality. In this talk, I will elaborate on these procedures, some of their properties and connections. To further investigate how these different mechanisms compare, we also pay special attention to the average and minimum rank of the resource obtained by the agents in the outcome allocation, providing both theoretical bounds on the loss potentially induced by these procedures with respect to these criteria, as well as an experimental study showing how different variants of swap dynamics behave. (This is joint work with Aurélie Beynier, Simon Rey, and Parham Shams. Companion paper available at https://arxiv.org/abs/1906.10250)
17:20 | Umberto Grandi (IRIT, University of Toulouse) - Kick-off talk of ANR project "Social Choice and Social Networks" (SCONE)
In this talk I will present the main line of research that we intend to investigate in the ANR SCONE project, which will last until 2023, to get feedback from the audience and scout for potential collaborations. The objective of this project is the conception of algorithms for opinion diffusion and vote computation in the presence of a social network, and its assessment in terms of computational and communication complexity, axiomatic properties, including game-theoretic ones such as resistance to strategic actions by voters or external agents.
18:00 | Closing
The PhD defence of Arianna Novaro will take place in the room Salle de thèses at the Arsenal Campus of the University Toulouse 1 Capitole.
The Workshop invited talks and coffee break will take place in the room ME001 at the Manufacture des Tabacs of the University Toulouse 1 Capitole.
This workshop is organized by Arianna Novaro, with the help of Umberto Grandi.
A question? Drop an email to arianna[dot]novaro[at]irit[dot]fr.